Following his wife's funeral, Bannion is offered protection for his threatened daughter - "round-the-clock detail" at his in-laws (Uncle Al and Aunt Marge) house where she has been taken for hiding: "It pays to play it safe." But he gets little additional help from either Lt. Wilks or Police Commissioner Higgins (Howard Wendell) concerning the investigation of his wife's murder when he demands: "Find out who planted the dynamite in my car." He accuses them of avoiding the larger conspiracy involving politicians, the police, and the underworld (led by Lagana who has everyone under his thumb) by intentionally delaying the investigation by looking into all his previous cases of homicides where he created enemies - "relatives and friends of killers you've sent to the chair - the motive was revenge."

Full of hate and personal vengeance, he accuses both of them of being intimidated and taking orders from Lagana. After pressing harder and provoking them, he is suspended from the force - and when Higgins demands his badge and gun, Bannion gladly tosses his badge on the desk: "You can have it, permanently." But he refuses to turn in his own gun: "That doesn't belong to the department." He vows not to use it in his relentless pursuit of his wife's killers:

I won't, not until I catch up with the people who murdered my wife.

In the next scene, Bannion vacates his now-empty and desolate house to take up quarters in a seedy hotel. As he moves out, his partner Gus Burke (Robert Burton) promises to help, as has Lt. Wilks, but off the record. Gus warns that Bannion appears to be on a "hate binge" toward everyone in the department:

Bannion: Look, I've had a belly full of the department and Wilks - and you.
Gus: ...You've decided people are all scared rabbits and you spit on 'em...No man's an island, Dave. You can't set yourself against the world and get away with it.

Bannion trusts no one, however, and rejects any help from the sympathetic fellow policeman. Conveying a sense of tearful loss, he takes one last glance at the bare kitchen where he shared so many happy moments with his wife. He closes the door on that idyllic chapter in his life.

An abrasive and rough Neanderthal, Vince returns to his plush penthouse apartment where his moll Debby is cha-cha-ing, mixing drinks, and narcissistically admiring herself once more in the mirror as he hungrily kisses her from behind:

Vince: What have you been doing all day?
Debby: Shopping.
Vince: Some career, huh? Six days a week she shops, on the seventh she rests, all tired out...Hey, that's nice perfume.
Debby: It's something new. It attracts mosquitos and repels men.
Vince: (He grabs her and swings her around.) Doesn't work that way with me.
Debby: It's not supposed to.

As the racketeer Lagana ("His Highness") enters, Debby is comparing her gangster/boyfriend (or Lagana himself) to a whip-cracking, domineering master of ceremonies at a circus: "He's a man with a big hat that holds up the hoop, cracks the whip and the animals jump through." True to character, Vince orders his brassy girlfriend to retreat to the kitchen, as Lagana remarks: "She's a young girl, Vince. Don't let her drink so much." Vince is a yes-man to Lagana and quickly agrees: "She keeps it up, she goes out of here on her ear. She's got no claim check on me." The implication that Lagana is responsible for the murders of Lucy Chapman and Mrs. Bannion is verified when Lagana, seated, expresses his upset at Vince's hired sidekick Larry for lousing up the two hit-contracts (disposing of Lucy Chapman's body and the attempted murder of Bannion):

Throwing the Chapman girl out on a county road brought us all the advertising we didn't want. Killing Mrs. Bannion. How stupid can you get?...Prisons are bulging with dummies who wonder how they got there. We can't afford people who make mistakes.

Lagana dismisses Larry and then speaks to his triggerman Vince as they walk to the penthouse balcony that overlooks the city's lighted skyscrapers. While surveying the territory that he controls, Lagana informs Vince that Bertha Duncan has upped her 'blackmail' "salary" demands to $500 a week. She will be paid as long as she withholds her husband's letter of confession from the police and keeps it in her safe deposit box. The fascistic Lagana is worried about the upcoming election, and doesn't want to upset citizen-voters with any more mistakes - especially when Vince offers to eliminate Bannion himself:

Vince, you worry me. We've stirred up enough headlines. The election's too close. Things are changing in this country, Vince. A man who can't see that hasn't got eyes. Never get the people steamed up. They start doing things. Grand juries. Election investigations. Deportation proceedings. I don't want to land in the same ditch with the Lucky Lucianos.

Lagana fears returning to his 'old-world' origins ("the same ditch with the Lucky Lucianos"). Bannion becomes fiercely committed to only one goal: revenge on the mobsters who are responsible for his wife's death. He really applies "the heat," threatening to tie big-time untouchable mob boss Mike Lagana to the killing of his wife. For a period of at least a week in a solitary struggle to pursue justice, he has been working his way through a list of mechanics in town who might have constructed the car bomb that killed his wife. At the Victory Auto Wrecking graveyard, he asks to speak to one of the employees, Raymond (Slim) Farrow (to ask him about the dynamite planted in his car). The very cool, closed-mouth, and uncooperative dealer, Mr. Atkins (Dan Seymour), tells him that Slim died three days earlier due to a "bad ticker." Bannion finds that Atkins is like all the others he has run into in the past ten years - another "scared rabbit" afraid to talk, and he was likely to have been on Lagana's payroll: "You wouldn't stick out your big fat neck for anybody."

As he leaves the auto yard, Selma Parker (Edith Evanson), a crippled secretary-clerk from the auto yard office who has heard his entire frustrating conversation with Atkins, approaches the persistent, trench-coated Bannion and offers the information Atkins withheld. [She is a perfect example of one of "the people" that is causing Lagana to worry. She is "steamed up" enough to fight back against crime.] She talks to him through the mesh-wire fence surrounding (and imprisoning her in) the yard, and reveals crucial evidence (the mention of a man named Larry and The Retreat):

There was a man came to see Slim about two weeks ago. They had a long talk out in the yard...He was about your height and he, well, he wore rather fancy clothes, you know, colorful...He came right into the office and asked me where Slim was...A man named Larry left a message once, just about the same time...He just said to tell Slim to call him at a place...He said to call him at The Retreat.

Grateful, Bannion thanks her for risking her life to help him. The scene dissolves from a closeup of Bannion's face behind the fence, to a view of his daughter's playtime baby-carriage and Raggedy-Ann doll - in the apartment of Bannion's in-laws. He visits his daughter there (who hasn't been told the truth of her mother's death). To help him discover the identity of Larry, he asks his brother-in-law Al (John Crawford) to phone The Retreat's phone number at exactly 9:30 pm and "ask for Larry" - so he can identify the man called to the phone. At 9:30 sharp, The Retreat's bartender answers the phone, but doesn't put the call through.

After that approach fails, at the same time, Bannion witnesses a hot-headed Vince Stone (with Debby sitting next to him and dressed in a mink coat) at the bar abusing a 'bar-fly' woman (Lucy Chapman's replacement) during a dice game for picking up the dice too soon - he extinguishes his lighted cigar on her hand. Bannion confronts Vince for his cruel treatment and insinuates that he tortured Lucy Chapman the same way:

Bannion: You like workin' girls over, don't ya?
Vince: Don't make a mistake, Bannion. Don't play hero with me.
Bannon: Maybe you're the one that worked over Lucy Chapman.
Vince: Take it easy, Sergeant. I don't know what you're talkin' about.

After throwing a few bucks at the bar-girl to buy herself "something nice," Vince quickly exits the club. His girlfriend Debby, who is impressed by Bannion's unglamorous style and courage, tries to be friendly and offers to buy him a drink at the bar, but he is cold to her: "With Vince Stone's money? I'd choke on it." She pursues him out to the street and confronts him - and then propositions him:

Debby: Do you get your kicks out of insulting people?
Bannion: Aren't you Vince Stone's girl?
Debby: The way you ask it, it sounds like a bunch of dirty words.
Bannion: (coldly) Well, that was the general idea. (She runs after him as he turns away and keeps walking. She walks backwards in front of him.)
Debby: Everybody's walking out on me tonight.
Bannion: What are you after?
Debby: I don't know. You, I think.
Bannion: Vince Stone chase you after me?
Debby: You saw him leave me in the bar like an old beer, or something. Come on, let's find out, I mean, if it's you I'm after.

Unfortunately for her, one of Vince's men notices Debby getting into a taxi with Bannion. She accompanies him to the Marlin Hotel and makes a friendly play for him in his stark, bleak hotel room. She critiques Bannion's shabby, seedy room with a sarcastic comment about its design:

Say, I like this: Early Nothing.

Naturally, her first inclination is to be drawn to a mirror where she fixes her hair. She removes her mink coat to reveal a low-cut black dress with cleavage. They have a Scotch and water together (from a prominent bottle), as she sits on his bed against plumped up pillows. Debby remembers how Vince worked her over once too (in their sado-masochistic, abusive relationship), like he did the bar-fly girl. She justifies the way she is sometimes treated by describing the rewards of the good life - her personal philosophy regarding money:

Debby: ...but most times, it's a lot of fun, expensive fun...He can be a pretty good guy, and then other times he can be - but why kick, you gotta take the bad with the good.
Bannion: Is the good good enough?
Debby: Clothes, travel, expensive excitement, what's wrong with that?
Bannion: Nothing, if you don't care where his money comes from.
Debby: The main thing is to have the money. I've been rich and I've been poor. Believe me, rich is better.

When Bannion exploitatively pumps the trashy woman for information about Larry or Lagana (he is the one who is conducting "research"), she becomes evasive and wants the questioning stopped. Appearing promiscuous and aggressive, a typical trait of femme fatales, she is obviously attracted to him and ready to come-on to him (her real reason for coming up to his hotel room is probably to spite her boyfriend), but she is put off by Bannion's hardened, unromantic and uncomplimentary mood:

Debby: I'd just stop the cross-examination. I didn't come up here to talk out of school.
Bannion: Why did you come up?
Debby: Well, why don't we call it research or something?
Bannion: Or to needle Stone.
Debby: Oh, well, you're about as romantic as a pair of handcuffs. Didn't you ever tell a girl pretty things? You know, she's got hair like the west wind, eyes like limpid pools, skin like velvet...?
Bannion: (He turns away from her.) I'll put you in a cab.
Debby: Did I say something wrong?
Bannion: No.
Debby: I must have broken one of the house rules. Do you really want me to go?
Bannion: I wouldn't touch anything of Vince Stone's with a ten foot pole.
Debby: That's a rotten thing to say. (She leaves with her mink coat draped over her shoulder.)

When Vince finds out that Debby has been seen with Bannion, he asks her about it when she returns to the penthouse that evening as he is again playing cards with his pals (including the Police Commissioner). Becoming a 'two-faced' liar, she is dishonest to him about her whereabouts, while she re-applies her lipstick in front of a mirror. Stone touches her cheek and observes: "That's a real pretty kisser." Jealous of her interest in Bannion and suspecting that she is giving out information, he insinuates that they had sex: "I thought maybe you and Bannion played footsie when my back was turned." In a malevolent rage, he viciously twists her arm behind her back and attempts to extract information from her: "You like cops do ya?...Where'd you go with him?...Oh, you pig, you lyin' pig."

In the film's most vivid and frightening scene, the dressed-up punk disfigures one side of her pretty face by flinging a pot of scalding hot coffee on her. He reaches for the bubbling Pyrex pot, and as the camera remains stationary on the burner, the soundtrack records the splash and screams as the left side of her beautiful face is scarred and burned. A victim of brutal violence, she rushes into the other room crying: "My face! My face!" Still carrying the pot, he follows her after the dastardly disfigurement and screams: "I'll fix you and your pretty face." While Commissioner Higgins takes her to the doctor, Stone calls Lagana and gets the OK, for "insurance" sake, to rub Debby out. Lagana wants to be assured that no trace of her remains: "But I don't want her found off any county highway. I don't want her found at all."

Realizing that she will be killed, and embittered because she has permanently lost her beauty (she sobs "I'm gonna be scarred"), Debby rushes to Bannion's hotel and begs to stay there. With one half of her face bandaged, she joins him in his quest for revenge against Stone (for throwing hot coffee in her face), king-pin Lagana and "Larry Gordon" - one of Lagana's men. She also implicates others, including the Police Commissioner, "Gillen from the City Council, George Fuller, Vince's lawyer, and Larry Gordon." When she realizes that he doesn't care about her when he asks, "Who's Larry Gordon," she tells him that the cop is partially responsible for the scarring she received because she was seen with him:

You don't care! You don't care what happened to me. You don't care about anything or anybody. I was followed when I came here with you. That's why I got this.

As she stands with her good profile toward the camera and has another drink of Scotch, she tries to accept her disfigurement:

I guess the scar isn't so bad, not if it's only on one side. I can always go through life sideways.

[Her sullied face reflects the duality of her character, and the connective link she exhibits between the two worlds.] And then she tells Bannion that Larry Gordon ("Gordon's the 'Larry' you asked about") is at the Wilton Apartments. (Bannion suspects that Larry is the "second-rate" gunman Lagana hired to help Vince kill Lucy Chapman and dispose of her body, and that Larry also hired Slim to plant the car bomb that killed his wife Katie.) He sincerely thanks her for the useful information.

Another closeup of a gun resting on a table opens the next scene at Gordon's Wilton Apartment door. To get a positive identification on Gordon, Bannion has the disabled Selma Parker step into possible harm by ringing his door buzzer. When she confirms his identity, Bannion rings again and slugs Gordon when he answers the door. Relishing the violence, he forces an incriminating confession from Gordon about all he knows that links Lagana and his mob to his wife's death. He strangles Gordon's with his hands around his throat to get him to "talk" and reveal that:

• Vince ordered him to get Bannion
• Gordon hired Slim at the auto junkyard to plant the car bomb that led to Katie's death
• Lucy was ordered killed by Vince because he was "scared" that Tom Duncan had "told her things"
• Bertha Duncan was "on the take" for years, but she wasn't silenced. In fact, she was "on the payroll" because she had something to blackmail Lagana with [her husband's suicide letter that details Lagana's corruption - enough to bring down his empire if exposed]

Bannion stops short of murder - he knows he doesn't have to kill Gordon: "I'm through with ya. But your friends aren't. I'm gonna spread the word that you talked. You're out of business, thief." Bannion puts the word out that Larry squealed, thereby guaranteeing his death.

In Lagana's mansion (the scene opens with the portrait of his mother), Vince reports that Larry has been killed (off-screen) for squealing while hurriedly attempting to leave town. According to Stone, Debby "doesn't worry" him. The hard-edged, steely Vince also argues that he shouldn't be made the "fall-guy":

If you had OK'd getting rid of Bannion, he wouldn't be a problem now. And when Duncan wanted out, I asked you to let me handle him. But oh no, you thought talking to him might keep him in line. So what happens, he knocks himself off. Don't make me the fall-guy, Mike! I'm no Larry Gordon.

Rather than killing Bannion ("If he knows anything, he's put it on paper. Anything happens to him, it becomes public property"), Lagana recommends kidnapping Joyce, Bannion's daughter: "Take something Bannion values more than himself and we keep him quiet." He plans to have the corrupt Commissioner order the police patrol away from Al's apartment building.

To extract more information about the level of Lagana's corruption. Bannion visits Mrs. Duncan once more. With the information Gordon had revealed to him, Bannion uses it against Bertha:

Furniture's the same. Nothing's been changed. You haven't started living high yet, have you?...Your husband was on Lagana's payroll. Now you are. You must have put down all the facts and figures in writing for Lagana to hold still for blackmail. What did you do with it?

He implicates her in Lucy Chapman's death ("You told Lagana about Lucy"), and accuses her of being happy when her husband blew his brains out. "A city is being strangled by a gang of thieves and you protect Lagana and Stone for the sake of a soft plush life." He grabs her and threatens to choke her as he did Gordon. He knows that her death will release the letter - and the "big heat" of police activity against the mob:

If anything happens to you, the evidence comes out. That's the way you arranged it, didn't you bright lady? You got it all put away someplace. That's how you kept Lagana over a barrel. But I'm not Lagana. With you dead, the Big Heat falls. The Big Heat for Lagana, for Stone, and for all the rest of the lice.

Police that have been alerted by Lagana arrive to protect her, and Bannion is forced to leave.

Bannion returns to his hotel, and to Debby's room where she has enveloped herself in the dark (the venetian blinds cast striped-shadows across her):

Debby: I've been feeling like something that's been shut up because nobody wants to look at it...Just sitting here thinking's pretty rough when you spent most of your life not thinking...
Debby: What was your wife like, Dave?
Bannion: (descriptively) 27 years old, light hair, gray eyes.
Debby: (eager to know more) That's a police description. Did she like to cook, like to be surprised, what kind of things made her laugh?...

Bannion remembers his wife as a saint and doesn't want to discuss her with Debby or with anyone. He tells Debby he almost killed Bertha Duncan an hour earlier. He implies that Bertha must be killed - by someone - to automatically lead to the publication of the written evidence Tom Duncan left behind. Debby reminds him that his nature is different from Vince Stone's - he's not capable of cold-blooded murder:

Bannion: He [Tom Duncan] left her a million dollar trust fund. Wrote down everything there was to know about the Syndicate.
Debby: Vince must hate her insides. He never could take losing or being pressured.
Bannion: He's got to take it. If she dies, the letter goes to the newspapers. You know. I almost killed her an hour ago. I should have.
Debby: I don't believe you could. If you had, there wouldn't be much difference between you and Vince Stone.

Just then, the phone rings and Bannion is alerted by Marge that the police's precinct detail hasn't arrived to protect Joyce. After tossing a gun at Debby "for company" - an overt prompting and indirect suggestion that she should kill Bertha Duncan - he rushes over to the apartment where a man confronts him on the dark staircase - with a gun pointed at his back. After a brief struggle, Al identifies Bannion to his army veteran buddies [the opposite of the audience's expectations] who were brought together to protect Joyce from Lagana's men. As Bannion leaves the well-protected apartment after accepting the domestic support of friends, he finds fellow officers Lt. Wilks and Gus arriving to provide the "official" police patrol as further support: "It's the first time in years I've breathed good clean air," Wilks admits.

Wanting to help Bannion, and afraid that he will kill Bertha and be arrested for murder, Debby gets her own revenge by going to Bertha Duncan's house to achieve the same purpose. Because she has been tarnished by her whoring association with the mob - and metaphorically damaged by that allegiance (one side of her face still reflects the ugly world of the gangsters), she decides to bring justice to Bertha. When Bertha hears her doorbell, she looks out through a curtained window and sees Debby's good-side profile facing her. Once inside, Debby notices that they are wearing similar mink coats. The expensive furs unite them as victims of a spreading disease - they are badges of ugly corruption and symbolic of the 'good-life' that they both bought with dirty money:

Bertha: Did Mr. Stone send you?
Debby: No. I've been thinking about you and me, how much alike we are. The mink-coated girls.
Bertha: I don't understand you. What are you here for, Miss Marsh?
Debby: Debby - we should use first names, Bertha. We're sisters under the mink.
Bertha: You're not making any sense, Miss Marsh. I'd better call Mr. Stone and have him pick you up. You're not well.
Debby: I never felt better in my life!

As Bertha tries to phone Stone at her husband's desk, Debby cold-bloodedly murders her with three gun shots and then tosses the revolver on the floor.

The next scene dissolves over the image of the revolver - Bannion's dirty work has been accomplished. He has his back to the camera as he stands in front of a downtown shop - across the street from Vince's penthouse building. In the store window's reflection, he sees Vince arrive in a gang vehicle. Debby has already returned to Vince's darkened apartment and waits there in the dark - to exchange the favor of face scarring and disfigurement. She splashes his face with hot coffee, scalding it, as he reaches to turn on the light. When she lightens the room, she is holding the Pyrex coffee pot and taunting him with a forecast:

It'll burn for a long time, Vince. (She hurls the pot away.) It doesn't look bad now, but in the morning, your face will be like mine. Look at it. It isn't pretty, is it? You'll walk through side streets and alleys so that people won't stare at you.

She rips off her face bandage to reveal the hideously burned left side of her blistered-face to him. She realizes the effect that the murder of Bertha Duncan will have - it will release the incriminating letter and ultimately destroy the gang and bring down Lagana's empire:

Oh, but you're lucky. It won't be for long. Bertha Duncan is dead. No more insurance for you and Lagana. The lid's off the garbage can, and I did it.

Stone retaliates by fatally shooting her twice in the back, just as Bannion arrives. Stone flees to the penthouse balcony, as Bannion finds Debby lying on the floor and dying. She confesses that she killed Bertha Duncan. On the penthouse terrace, Bannion has a final gun battle with Stone and mercilessly beats him - he slowly raises his revolver to kill Stone - as the criminal dares him: "Go on, SHOOT! SHOOT! SHOOT!" But Bannion lowers his gun after deciding he can't commit the murder himself. Wilks and Gus arrive to arrest Stone and take him into custody - for the attempted murder of Debby. Bannion suggests that the police now have the evidence they need to jail the entire corrupt Syndicate:

Put a cover on Lagana, Higgins and every other thief in town. Duncan left a confession. It'll come out now. The lice will try to run.

Debby's friendship, civic-minded courage and sacrifice have had a profound effect on Bannion. Sympathetically, he cradles her head with her mink coat. Although she is attended by a doctor, she realizes that she is dying, as he kneels at her side. She pulls up her mink coat to hide the disfigured, hideous side of her face in its pillow - he regards her from her 'good side':

Debby: I'm gonna die...I don't want to die. I must look awful. Vince should have never ruined my looks. It was a rotten thing to do. Dave... I'm gonna die...Remember how angry you got when I asked you about your wife?
Bannion: (without anger or hate in his voice) I wasn't angry. You and Katie would have gotten along fine.
Debby: What was she like?
Bannion: A real Irish blow-top, but she always got over it fast. She used to raise the roof with me for missing dinner, or leaving the bathroom in a mess. A few minutes later, she'd come in with a drink in her hand for me just as if nothing had happened. You know, Kate, she was a sampler. She'd take sips of my drink and puffs on my cigarette, and sometimes she used to taste the food off my plate. I got a big kick out of that.

Because Debby gave her life (like his martyred wife), avenged his wife's death, and tried to change and adopt a decent life, Bannion is now willing to treat her lovingly and comfort her. He talks to Debby about Katie, their marital relationship, and how they led a loving life - often sharing food or drinks. Debby expresses a peacefulness in her final words, referring to Bannion's murdered wife:

I like her...I like her alot.

Even after Debby dies and achieves a degree of 'salvation,' he expresses the healing effect of reform. Bannion smiles as he idealistically remembers more about his "birthday-cake" wife, his "princess" daughter, and their blissful family life:

Sometimes when I came home from work, she'd have the baby dressed up like a, oh, like a princess. One of the most important parts of the day was when I came in and saw her looking like something that just stepped down off a birthday cake. I guess, I guess it's that way with most families.

The Kenport Courier newspaper headlines dissolve into view:

LAGANA, HIGGINS INDICTED!
Duncan Confession Exposes Crime Syndicate

By the film's conclusion, Bannion has left behind a wide wake of death and destruction - four women have lost their lives, he has lost his home, and his daughter's life was threatened, but the underworld Syndicate has been broken, the mobsters are taken into custody or eliminated, and Commissioner Higgins is in jail.

A vindicated Bannion, restored to good standing in the Homicide division of the police force, puts blind hate and revenge behind him and returns to his desk job on the force. [There is no further reconciliation of the widowed hero with his daughter or a re-establishment of home life.] He restores his name plate to his cleared-off desktop, is offered coffee, and given newly-sharpened pencils for further work. As the film ends on a cautious note, Bannion is called to go out to investigate another case (a hit-and-run accident on South Street) - the battle against crime, a pestilence that forever percolates, never ends. He passes the poster entreating: GIVE BLOOD NOW, as he calls out for a symbol of domesticity to be returned to the stove until his return (an ironic ending in a film with two boiling coffee scaldings):

Keep the coffee hot, Hugo.