Elsa drives her open convertible up and down steep hills in San Francisco (on Sacramento and Mason Streets) to the Hall of Justice (at Kearny and Washington Streets). She meets her husband in the lobby outside the courtroom, close to where Michael is jailed. During a very slow-moving dolly shot toward them and as the famed lawyer is often interrupted with greetings from his corrupt law acquaintances, the Bannisters have a disagreeable and hateful dialogue about Michael's innocence and Grisby's alleged involvement and plot to fake his own death. Bannister seems determined to make sure that O'Hara is convicted. (Elsa smokes during the scene - something she learned since meeting Michael that clearly associates her with him.) Evidence doesn't help Michael's case - the gun that killed Grisby cannot be found. Although he has never lost a case, Bannister doesn't mind seeing Michael found guilty, but he doesn't want his wife to view a convicted Michael as a martyr:

Bannister: Isn't it your idea to save Michael from the gas chamber?
Elsa: Arthur Bannister's the only one who can do it...
Bannister: I was the murdered man's partner. The other victim was my servant. If I defend Michael, any jury is going to figure I have reason to believe that he's innocent.
Elsa: And you have reason to believe that Michael is innocent?
Bannister: I, uh, I hear that Galloway [the District Attorney] (Carl Frank) is going to say that Michael took George's corpse into the city in our speedboat.
Elsa: But he didn't. We can prove...
Bannister: Prove? George couldn't have taken it.
Elsa: Why not?
Bannister: Well, how could he get back?
Elsa: Back where?
Bannister: The yacht, naturally. The speedboat couldn't have driven itself. Or maybe it was George's ghost. Maybe the boat just drifted back. No, lover. Michael has got to plead excusable homicide.
Elsa: But you can prove he didn't do it with his gun. They already know it wasn't Michael's gun that killed George.
Bannister: The gun that did kill George can't be found, lover. So we can't prove that Michael didn't shoot him. And it was Michael's gun that killed Broome. No, Michael is going to need everything the 'greatest living trial lawyer' can do for him. Our good district attorney over there has worked up a beautiful case: the truck driver, the fat saloon keeper down at the docks, they'll be effective witnesses. And he will know how to handle them. And then there's this, uh, crazy confession.
Elsa: But Michael has an explanation.
Bannister: (chuckling) Explanation?
Elsa: You think it's funny.
Bannister: Funny? You mean that story about how George hired Michael to kill George.
Elsa: To pretend to kill him.
Bannister: Really? Why would George want to disappear?
Elsa: Michael said something about partnership insurance.
Bannister: What?
Elsa: Partnership insurance.
Bannister: Which he, George, wanted to collect?...And he, George, wanted everybody to think he was dead?
Elsa: Yes.
Bannister: Dead, so that he could collect the insurance?
Elsa: Yes.
Bannister: Well, if he was dead, how could he collect? No, lover, if your Irishman doesn't want to go to the gas chamber, he's got to have to trust me.
Elsa: But you. Do you trust him?
Bannister: I wouldn't trust him with my wife.
Elsa: You want to make sure he doesn't get off, don't you?
Bannister: I've never lost a case, remember? Besides, my wife might think he was a martyr. I've got to defend him. I haven't any choice. And neither have you.

Allowed to visit Michael in his jail cell alone (by her husband), Elsa speaks to him but is separated by upright black bars and a screen. O'Hara feels doomed to die, but Elsa encourages him to "trust" her husband - "because it's your only chance - because I want you to." When she advises him to admit to his murder of Broome (does she really believe this?), Michael explains that Grisby killed Broome and wanted to murder Bannister too, because "he couldn't get a divorce...so he could get away from his wife." She expresses her profound doubt about Grisby faking his own death - a close-up displays her stunned expression as she tells him: "George didn't have a wife. He wasn't married."

An unforgettable, farcical courtroom scene (a vaudevillian theatre of the absurd) makes justice seem ludicrously administered: there are frequent coughing and sneezing fits in the crowd and jury box; bouts of laughter from a disruptive audience that views the proceedings as entertainment; a fat gallery attendee sleeping; two gum-chewing observers, one of whom sticks her wad under her chair; two talkative Chinese girls gabbing in their foreign tongue about the trial (ending with "You ain't kiddin'!"); a jury member guffawing inappropriately when Bannister is identified as "a member of the bar," etc. The trial opens with Bannister loudly objecting to the befuddled presiding judge (Erskine Sanford) about the questioning of a police officer by the district attorney:

Bannister: I object! The question calls for the operation of the officer's mind!
Judge: Sustained.
District Attorney: Very well. In the interest of saving time, we will proceed. As I'm sure Officer Peters is most anxious to go home to his wife and family before returning to duty. Now then, Officer Peters, except for the blood, the clothes were dry...Yet the defendant stated in his confession that he threw the body into the bay. [The written confession about the body being thrown into the bay should discredit the entire statement.]
Bannister: Your Honor, the District Attorney isn't cross-examining, he's making speeches.
District Attorney: That simply isn't so.
Bannister: I move for a declaration of mistrial be sought on the grounds that the jury is being prejudiced.
District Attorney: These are some of the great Bannister's 'trial tactics.' In an appeal for sympathy...
Bannister: The District Attorney is beginning to get vicious.
Judge: When you two gentlemen get over your argument, tell me who won. Then I'll decide on the objection. (Laughter) Objection sustained.

Bannister completely discredits Officer Peters' entire testimony (and the D.A.'s appeal for sympathy) by stating that Officer Peters doesn't have a wife or children. The D.A. then calls attorney Bannister to the stand as a witness, to testify against his own client. The questioning about Michael's activities quickly degenerates into a shouting match about improper tactics (with strident accusations of each side about making speeches and drawing conclusions) - and an appeal for a mistrial.

Meanwhile, a concerned and modestly-elegant Elsa looks warmly at Michael. Bannister argues that he should be allowed to cross-examine himself (prefacing statements with QUESTION: and ANSWER:) about Michael's virtues, thereby making the trial even more humorous. Elsa is served a subpoena, called as a witness, and questioned about the murdered Sidney Broome (who was employed by her husband as a detective in divorce cases and who also served as a butler in the household and steward on the yacht). As she perches above everyone in the witness box, it is insinuated by the confrontative D.A. that a suspicious Bannister hired Broome to "watch" her - during a period of mutual infatuation with O'Hara. As the courtroom hushes and attentively leans forward for Elsa's answer ("He was very respectful...and I think he was fond of me..."), her face fills the screen as she admits to kissing and loving Michael - in public view - at the aquarium.

During jury deliberations over "the fate of Black Irish O'Hara, the notorious waterfront agitator", the ineffectual judge, reflected in a window overlooking a panoramic view of the Bay Bridge and Ferry Building), plays a solitary game of chess and hums to himself in his chambers - an apt symbol for the fateful, kangaroo court proceedings (an overhead view of the courtroom verifies the association). Just before the verdict is announced by the jury, however, O'Hara is coaxed, by Elsa's glance and non-verbal gesture, to take an overdose of Bannister's pain-killing pills that are in the foreground, after "tough"-guy (but weak defense lawyer in this case) Bannister gloats to him:

This is one case I've enjoyed losing. I'm coming to see you in the Death House, Michael, every day. Our little visits will be great fun. I'm going to ask for a stay of execution, and I really hope it will be granted. I want you to live as long as possible before you die...I've got an edge. I know you're going to the gas chamber.

After Michael downs a handful of pills, confusion and bedlam erupt in the courtroom. Guards drag him into the judge's chambers where they attempt to "keep him moving" and walk off the effects while a doctor is summoned. When he is able to overpower two guards (numerous articles of glass are shattered in the office), he escapes from the building by posing as part of another jury (from another trial about a jewel robbery) on their way to lunch. He is given a sudden fright when a guard shouts at him for listening to another jury member discussing the trial. O'Hara's main objective in his flight (across Portsmouth Square and north on Grant Avenue from Pine Street) is to try and find the gun (and the murderer) that killed Grisby. High above, Elsa watches his exit from a courtroom window.

He flees into the Chinatown district of San Francisco where he ducks inside the Sunsing (or Mandarin) Theatre during the performance of a costumed, stylized Oriental melodramatic opera. Elsa has no difficulty following, since she has a command of fluent Chinese and can ask bystanders about his passage. Backstage in the theatre, she telephones her Chinese servants and Li to come to their aid ("to arrange...someplace to take you," she soon tells Michael). She finds him in the audience, the only Westerner in attendance among other wizened spectators, and sits next to him. He admits to being "faint" from the effects of the pills. As they embrace (Judas-style) to avoid being discovered by authorities and she advises him: "don't move," the eyes of the masked or heavily made-up actors on stage dart back and forth when they see the police in the aisles.

Michael discovers the gun that killed Grisby is in Elsa's possession in her handbag. Just before he passes out, he denounces her as a blonde Circe - as he sticks the gun into her ribs:

You killed Grisby, yes. You're the killer.

He is dragged away, kidnapped by Elsa's servants, and taken to a hideout - a deserted funhouse/amusement park closed for the season. One of the greatest visual effects in cinematic history is in this final sequence of the film - the famous Crazy House/Hall of Mirrors scene. As Michael awakens after being taken there by Elsa's accomplices, he explains the full murder plan - in voice-over, as he hallucinates:

I was right. She was the killer. She killed Grisby. Now she was going to kill me. Her servant Li and his friends smuggled me out into the darkness and hid me where I'd be safe from the cops, not safe from her. One of the Chinese worked in an amusement park. It was closed for the season. An empty amusement park makes a good hide-out and she wanted me hidden. Well, I came to in the Crazy House and for a while there, I thought it was me that was crazy. After what I'd been through, anything crazy at all seemed natural. But now I was sane on one subject - her. I knew about her. She planned to kill Bannister, she and Grisby. Grisby was to do it for a share of Bannister's money. That's what Grisby thought, but of course, she meant to kill Grisby too after he'd served his purpose. Poor howling idiot, he never even did that. He went and shot Broome, and that was not part of the plan. Broome might have got to the police before he died. And if the cops traced it to Grisby, and the cops made Grisby talk, he'd spill everything and she'd be finished. So she had to shut up Grisby but quick. And I was the fall guy.

[The murderer and mastermind of the whole affair turns out to be the villainess Elsa, in true film noir fashion - she literally 'shanghai's' him. She had planned to kill her husband (with co-conspirator Grisby) for a share of the money, then kill Grisby and frame Michael for the crimes. From his vantage point, Grisby was expecting to disappear (with partnership insurance) with everyone presuming he was dead - after Michael had 'murdered' him. But when Grisby killed Broome, she knew that the plan would fail so she killed Grisby herself - off-screen - (or warned Bannister to kill Grisby?). Michael realizes that he was duped by Bannister, Elsa, and Grisby as they circled around each other like sharks - and made him their fall guy.]

Wondering if he is "crazy" or not, he walks through a hallway before a moving web of black shadows, a fragmented drawing of a wild horse, a grotesque sign reading "STAND UP OR GIVE UP", and other angular, expressionistic surroundings reflecting his mental instability. He trips a mechanism in the "Crazy House" and careens down a long, zig-zag slide or chute past a menacing, thirty-foot high dragon's mouth halfway down. After descending the labyrinth, he emerges into the Hall of Mirrors on a rotating, unstable floor. The Hall of Mirrors (the Magic Mirror Maze) is constructed with myriad mirrors - huge, distorted closeups mingle with multiple fragmented images.

Blonde, dark femme fatale Elsa, appearing in a shadowy doorway, shines her flashlight at his face. As she confesses her guilt to him, she exhorts him to understand why she duped him and was fated to frame and betray him. [Her guilty wrong-doings are never shown on-screen, only the consequences.] She vows her love for Michael without directly answering his question: "You and me, or you and Grisby?" He restates her earlier proverbial statement - challenging her to aim for "something better" than her original nature [to STAND UP rather than GIVE UP], but she declines. She believes in following her "original nature (to) the end" (i.e., satisfying her greed and pretending to love him) rather than truly loving him:

Elsa: Why don't you try and understand? George was supposed to take care of Arthur, but he lost his silly head and shot Broome. After that, I knew I couldn't trust him. He was mad. He had to be shot.
Michael: And what about me?
Elsa: We could have gone off together.
Michael: (cynically) Into the sunrise? You and me, or you and Grisby?
Elsa: I love you.
Michael: One who follows his nature keeps his original nature in the end. But haven't you heard ever of something better to follow?
Elsa: No.

A moment later, her brilliant, crippled husband arrives - walking with his gnarled canes. His image is prismatically multiplied a dozen times in a layered series of vertical panes. He confronts the deceitful couple and then vengefully threatens his rotten wife with a letter he has written to the D.A. explaining her guilt and Michael's innocence. He also threatens to shoot her ("I'm aiming at you, lover"). Surrounded by myriad, countless images (all of their illusionary, multiple identities) that they will shoot to bits, Bannister bemoans the fact that their self-canceling killings will be indistinguishable ("killing you is killing myself"):

I knew I'd find you two together. If I hadn't, Elsa, I might have gone on playing it your way. You didn't know that, but you did plan for me to follow you...I presume you think that if you murder me here, your sailor friend will get the blame and you'll be free to spend my money. Well, dear, you aren't the only one who wants me to die. Our good friend, the District Attorney, is just itching to open a letter that I left with him. The letter tells all about you, lover. So you'd be foolish to fire that gun. With these mirrors, it's difficult to tell. You are aiming at me, aren't you? I'm aiming at you, lover. Of course, killing you is killing myself. It's the same thing. But you know, I'm pretty tired of both of us.

As Bannister (Elsa's cruel pimp husband) and Elsa (a beautiful femme fatale) self-destructively draw their guns and shoot at multiple likenesses of each other, the screen erupts into a wild kaleidoscope of smashed glass, cracked and chipped pieces of mirror, and shattering bits of their false images. Their aim is confused by the contradictory mirror images that break into splinters during the wild shooting as one fake image splinters and another replaces it. Witnessing the double murders as he steps back and watches them destroy each other, Michael is horrified by the shattering of glass as the deceptive facades of their evil images are reflected and then blown away - and all that is left in the violent shoot-out is their guilt, greedy hunger, pain and misery. They finally are able to break through all their surfaces until they mortally wound each other. At its climax after the panes have been blasted away, both Bannister and Elsa are dying and face each other across a scene of shattered glass. Still in character, Bannister remarks:

You know, for a smart girl, you make a lot of mistakes. You should have let me live. You're gonna need a good lawyer.

Elsa stumbles with Michael into another room. The camera films at ground level down next to Elsa on the floor, as she agonizes over her death. While she is dying, she has one last exchange with Michael. He recalls their conversation in the streets of Acapulco about the badness of the world, and his fishing tale about blood-thirsty sharks. After she admits her own "original nature" delved into corruptness and evil and surrendered to "badness," her pleading fails to gain his sympathy, even after an appeal to his sentimentality:

Elsa: (gasping) He and George, and now me!
Michael: Like the sharks, mad with their own blood. Chewing away at their own selves.
Elsa: It's true. I made a lot of mistakes.
Michael: You said the world's bad, and we can't run away from the badness. And you're right there. But you said we can't fight it. We must deal with the badness, make terms. And then the badness'll deal with you, and make its own terms, in the end, surely.
Elsa: You can fight, but what good is it? Goodbye.
Michael: You mean we can't win?
Elsa: No, we can't win. (poetically) Give my love to the sunrise.
Michael: We can't lose, either. Only if we quit.
Elsa: And you're not going to?
Michael: Not again!
Elsa: Oh Michael, I'm afraid. (He strolls away.) Michael? Come back here. Michael! Please! I don't want to die! I DON'T WANT TO DIE!

Unhooked from her charming and fatal attraction, Michael abandons her to die alone. As he leaves, the revolving exit gate makes a death rattle as it rotates. He walks away from the corpses (the two dead sharks left from the blood-lust), and emerges renewed to life - released out of the dark fun house's nightmare into the dawn's air and light next to the beach. As he walks across the street to call the police and the camera slowly ascends, the "innocent" (or stupid-minded) sailor reflects and narrates to himself about how he will be proven legally innocent and exonerated by Bannister's letter. Although corrupted by being made bait (the fall-guy) between a wealthy (but greedy) bunch of tough sharks, he predicts that he may become more ambivalent, forget Elsa and put her corruptive influences behind him - if he grows old enough:

I went to call the cops, but I knew she'd be dead before they got there and I'd be free. Bannister's note to the DA (would) fix it. I'd be innocent officially, but that's a big word - innocence. Stupid's more like it. Well, everybody is somebody's fool. The only way to stay out of trouble is to grow old, so I guess I'll concentrate on that. Maybe I'll live so long that I'll forget her. Maybe I'll die tryin'.