The Springfield Herald News displays front-page headlines with a grim, mug-shot photograph:

To catch Jarrett, Evans goes along with Cody's deceptive ploy. The T-man plans to use undercover agent "copper" Hank Fallon (Edmond O'Brien), a frequent choice for an "undercover specialist." The police informant brags about his last job - he recently shared a cell with a "most talkative little con" at San Quentin Prison, resulting in sending the "whole syndicate" up for trial in a few weeks. He compares his job to catching fish - as he fiddles with a fishing pole reel in his hands:

You put it on a pole, wind a spool of silk thread around it, and you hold the pole over the water. Then you sit under a nice shady tree and relax. After a while, a hungry fish comes along, takes a nip at your hook, and you've got dinner. For the next two weeks, I'm not gonna think about anything except the eternal struggle between man and the fish...Phil, look at me. College degree, lovable personality, and I spend most of my time in prison, an undercover specialist. Eight sentences in five years! Dannemora, Sing-Sing, Leavenworth. I joined the Department to put criminals behind bars - and here I am, stir crazy!

A teletype message from Springfield, IL describes a police report from the Springfield authorities: "Cody Jarrett Confession Checks...Will Be Sentenced on Twenty Eighth." Fallon angrily explodes, knowing that Jarrett is getting away "with a two-bit prison stretch." It was Evans' plan all along, however, to accept the "phony rap" in Illinois and then plant Fallon as an informant in the Illinois prison.

Cody's racket is a sophisticated one - it involves stealing federal money and re-selling (money laundering) it through a fence (or "Trader") for a profit on the European black market. Fallon's job is to buddy up to Jarrett as one of his cellmates in prison, to find out the location of the stolen $300,000 dollars, and figure out the identity of Cody's Trader fence:

Fallon: A hoodlum turns himself in on a phony rap and beats the gas chamber. I'll betcha he's thumbing his nose at Uncle Sam right now and loving it. Jarrett outsmarted you!
Evans: That's just what we want him to think. We're working with the Springfield police. We arranged for the confession to check. So what happens? Jarrett does a stretch in the penitentiary - and in case he gets lonely, wants to talk to someone, we're gonna let one of our own boys do a stretch right in the same cell. Still going fishing, Hank?...You'll be committed to the penitentiary in Illinois. You'll be one of Jarrett's cellmates. Stick with him until you find out where he unloaded $300,000 dollars in federal currency without a single bill showing up. Also, try to learn the identity of the very special fence that engineered this deal.
Fallon: How does he operate?
Evans: Buys stolen money here at thirty-four cents on the dollar. Peddles it on the European black market for - who knows how much. No questions asked. Sweet racket.
Fallon: In step with the times.

Into the evening, Fallon scrutinizes the photo and case history prison records from Illinois of hundreds "of the roughest and toughest," and they decide to weed out two inmates who would recognize him and needed to be transferred. And Fallon rehearses the story of his arrest - "I'll be picked up in a joint known as...Bill's Hideaway on what seems like an ordinary hood roundup. One of the boys spots me as a lamister. I make a break for it. When I pick myself off the floor, I'm meek as a baby." Information will be passed out regularly with visits from his "wife" on visiting days. One inmate named "Bo" Creel is a cause for concern, since Fallon arrested him two years earlier: ("Bo Creel would know me in the dark"). But then they dismiss the concern: "We don't have to worry about him. Finishes his stretch Saturday. He'll be out before you're sentenced."

Evans cautions Fallon about the case - Cody is a homicidal, abnormal, psychopathic mama's boy who faked headaches when he was a boy to get his mother's attention, but then grew up with real, painful headaches. Both his father and brother died insane. Possessing a mother complex, he is now obsessively devoted to his mother, a shrewd woman who has master-minded his criminal career as a gangster and used her son (as her husband-substitute) to seek vengeance on the world:

Evans: This job isn't gonna be like any of your others, Hank. You see, there's insanity in the Jarretts, and some of it rubbed off on Cody. His father died in an institution...When he was a kid, he used to fake headaches in order to get his mother's attention away from the rest of the family. It worked. As he grew up, the fancied headaches became real, until now they tear him to pieces. Any minute, he's apt to crack open at the seams. And there goes our case. So you'll be workin' against time...Except that Cody's not an easy guy to get close to in a hurry. The only person he's ever cared about or trusted is his mother. No one else has ever made a dent, not even his wife. His mother's been the prop that's held him up. He's got a fierce, psychopathic devotion for her. All his life, whenever he got in a spot, he just put out his hand and there was Ma Jarrett. Without her, maybe Cody'd - just like his old man.
Fallon: You mean I'm supposed to take Mama's place?
Evans: You never can tell. He might need someone.
Fallon: I'll practice up on my lullabies.

In a Superior Court in the State of Illinois, a Judge (George Spaulding) sentences Cody for the crime of grand larceny at the Palace Hotel to a term of "not less than one and not more than three years in the state penitentiary." Hank Fallon, now posing as small-time crook Vic Pardo - the next criminal to be sentenced, brushes by Cody as he passes by him into the court, asking about the Judge: "How is he? Tough?"

In the prison courtyard during a mid-day break, Cody has his hard-of-hearing lifer cellmate Herbert the Reader (G. Pat Collins) lip-read the spoken words of another prisoner Roy Parker (Paul Guilfoyle). Parker's conversation reveals that Jarrett's #1 right-hand man, Big Ed, has taken over the gang - and also has designs on Verna: "It's about Big Ed...He's the number one boy now, Parker says, in more ways than one."

Instinctively suspicious of strangers, Cody doesn't trust Pardo, another one of the new prisoners:

I been watching you and up to now, you haven't done anything I can put my finger on, but maybe that's what bothers me. But I don't know ya, and what I don't know I don't trust. To me, you're just a face and a number, and let's keep it that way for now. When I want your help, I'll ask for it.

In a line-up of new prisoners for shots in the dispensary of the prison's hospital ward, including both Jarrett and Pardo, Bo Creel (Ian MacDonald) dabs alcohol on the upper arms of the convicts.

[Note: In a surprising revelation, it is learned that Creel's expected departure from the prison was delayed on account of a case of pneumonia. He planned to be dismissed from prison the next day after being checked by the doctor. He would undoubtedly recognize Fallon/Pardo.]

When Cody approaches, he asks Creel for a favor after he gets out: "Look up Big Ed. Tell him I was askin' for him." To avoid being recognized as an infiltrator by Creel, Pardo instigates a fight with Parker behind him in line by punching him in the mouth. As punishment, he is cooled off in solitary confinement for a month.

When Pardo is released and returned to his cellmates, Cody, Herbert the Reader, and Maddox, he narrowly averts being detected twice. He doesn't instantly notice a large photo of his dark-haired wife ("Margaret Baxter") that the convicts have prominently displayed in the cell. Only after finding the opened large envelope on his top bunk addressed to him, and exercising some quick thinking does he exclaim that he didn't recognize his wife in the photo because she changed her hair color. He also tenses up when Cody grins and states:

Cody: Too bad your little trick didn't work, Pardo.
Pardo: (grunting) Huh?
Maddox: Doc says you gotta take your shots anyway.

During his confinement, Cody learns from cell neighbor Benny (via Parker) through the Reader (using a mirror to read Benny's lips) that his gang's "boys pulled a caper" that netted "fifty-seven grand." Cody confidently feels that he will still get his full share with Ma in charge: "Ma sees to that." Cody's face dissolves into his mother's - symbolic of their unified will. Around a table with stacks of distributed money, Ma preaches to the entire gang - Het, Cotton, Happy, and Big Ed - during Cody's absence:

Get one thing clear, all of ya. Anything we get, Cody's in for his full share. That's how it is. Anyone thinks different, say so now. Or would you rather wait till Cody gets out? Well, any argument?

Verna was disgusted and sullen over Big Ed's weak acquiescence toward Ma's direction of the gang and her decisions regarding Cody's cut of the take; sulking, Verna leaves the group "to pick strawberries." With Cody in prison, she has easily switched allegiances to Big Ed, but now wonders about his spinelessness - she reprimands him on the front porch:

Big Ed: What's eatin' you, sugar?
Verna: You and your big ideas! That's all they are - ideas! 'You and me belong together, sugar. Just leave it to Big Ed.' Well, I'm sick of waitin' for you to make your move. You're as scared of Cody as any of 'em. He's still Mr. Big - in prison or out.
Big Ed: What makes you think so?
Verna: (sarcastically) You. Fair is fair, is it? That's quite a beef you put up about Cody being in on the cut.
Big Ed: See, a guy who thinks his pals is taking care of him - he gets kinda careless.
Verna: What does that mean?
Big Ed: Alive, Cody gets out in one, two years, maybe. Dead, he gets out sooner.
Verna: Dead?

Big Ed has 'ideas,' however, and has arranged for Cody to be killed in prison: "Right now, he's a sittin' duck up there in that pen. He's rubbin' elbows with a guy that does anything I say." She asks: "When, Ed?" He answers: "When I say so." Big Ed spits out his gum before kissing Verna, just as Ma Jarrett peers out at their conspiratorial session through a window.

Cody's job in prison is to collect small trash bins with metal shavings in the machine shop, filled with lathes, stamps, presses, drills, and boring machines. Roy Parker, Big Ed's man on the inside, deliberately moves a big metal trash bin out into the open, thinking himself unobserved. Above the bin is a large monorail used for transporting heavy equipment, with winches, claws, controls, and hooks operated by Parker. From the moving pulley hangs a heavy transformer weighing a few hundred pounds - moving ominously directly over Cody's head. Sensing that Cody will be crushed by the fall of the heavy object, Pardo leaps and hurtles his body toward Cody, tumbling him to the ground just as Parker disengages the hook holding the transformer. Parker trembles with an excuse to one of the guards regarding the accident: "The lever slipped." Cody is enigmatically ungrateful to Pardo for saving his life:

Pardo: I saw that just in time.
Cody: Whaddya want - a medal?
Pardo: You woulda looked like that barrel.
Cody: You almost walked into it yourself. Why should you care if a guy named Cody Jarrett gets his, if ya don't want somethin'?
Pardo: OK, keep your medal.

Called to the Visiting Room for an unexpected visit from his Ma - although separated from her by a wire screen, Cody is told by his strain-faced, nervous mother that he has been betrayed, understandably, by Big Ed:

Ma: I'm the one to tell ya. It's Big Ed and Verna. They run out. It's my fault, Cody. I let you down. I said I'd take care of things. But I let ya down. I saw it comin'. I didn't think he'd have the guts.
Cody: Forget it, Ma, forget it. It was in the cards for Big Ed to make his try.
Ma: Don't ya care?
Cody: Sure. What's mine is mine. I ain't gonna have it make me sick. I'll take care of 'em when I get out.
Ma: That's what I told myself. And I'll help ya Cody, like always. You'll be out soon, back on top of the world.

She surmises with her son that "tinhorn" Big Ed has made his "move" and ordered his pal Parker to "accidental-ly" drop the heavy-duty equipment on him. Ma knowingly responds: "He was figurin' you'd be dead." In her gnarly, flinty voice, she vengefully promises to get even and "take care of" the treacherous Big Ed on the outside before Cody's release:

Ma: Any time I can't handle his kind, I'll know I'm gettin' old. No one does what he's done to you, son, and gets away with it.
Cody: No, no, Ma, look, listen to me, you won't have a chance.
Ma: I'm goin' after him, Cody, to keep him from having you knocked off in here.

He grips and clenches his fingers around the wire screen separating him from his mother, impotently pleading with her to stay away from Big Ed: "I'm tellin' ya, don't do it..., Ma, Ma, Ma!"

Back in the machine shop, Cody broods and then speaks to Parker: "What's the matter, Parker? I ain't gonna do anything. Not now. I'm gonna let you stay awake nights and sweat it out. Then when I get ready, good and ready, I'll pay ya back." Cody repeatedly hears his mother's voice ringing inside his head and replays her words: "I'll take care of him, Cody." Things begin to blur in his vision, and the shop machinery takes on threatening shapes. The screeching of the machines portray Cody's mental state. His eyes spin round as the blinding pain seizes his head, and Cody falls to the floor. Crawling over to Pardo, Cody begs: "Cover for me, cover for me!" so Pardo overturns a toolbox onto the floor. As Cody's surrogate mother through transference, Pardo rubs the back of Cody's head to ease the pain and wipe away the painful headache:

Don't let it beat ya, Cody. You're top man, aren't ya? Ever since I was a kid, I've been readin' about ya, always hopin' I could join up with ya. You don't wanna let a bunch of two-bit mugs see Cody Jarrett down on his knees, do ya?

When the pain has subsided, Cody finally acknowledges Pardo's friendship and befriends the hero-worshipping criminal, taking him into his confidence and trust.

During a moonlit night in their cell, Cody spends a sleepless night, ruminating about his Ma: "She's walkin' into trouble." Rather than "sittin' out this penny-ante stretch," that was part of his plan to "take the heat off me for another job," Cody is planning an imminent crash-out to take care of Big Ed on the outside: "Sometimes ya make plans and sometimes they don't work out. Then you gotta get to it - fast. Ya understand?...I got business on the outside." With a plan to "fix the generators" that "control everything - searchlights, gun turrets, main gate," Pardo conspires to assist Cody "without artillery" (a gun stashed away by inmate Tommy Ryley (Robert Osterloh)), and insists that they escape as a pair: "...we gotta do it alone." During a visit with his 'wife' the next day - Margaret Baxter (Fern Eggen), Pardo relays the escape plan to Evans through his contact: "Tell Evans we'll break out Thursday night. Tell him to plant a car with an oscillator."

Agents in Evans' office discuss the getaway plans and the planting of a getaway car in the trees with an oscillator attached under the car's rear axle and hooked up to the battery. Once the escaped cons begin traveling in the car, they will be tracked by the oscillator that will pick up a transmission radio signal on wavelength forty-seven point one, enabling the agents to crossplot their exact position if they are within a 20 mile radius: "It doesn't matter how far they travel. As long as our cars are within receiving distance we can tell where they are."

Hundreds of prisoners file into the prison mess hall (in a long shot from an upper tier high above where armed guards patrol the perimeter) - it's a prelude to one of the best scenes in the picture. After all the prisoners reach their places, a whistle is blown to signal them to sit. Prisoners are forbidden to speak to each other, although Pardo whispers "tonight" to Cody - the expected time for their breakout. One of the new prisoners at the end of Cody's table is Nat Lefeld (Eddie Foster) "from the Coast mob" - Cody relays a message: "Ask him how my mother is." Through a whispered, inaudible grapevine message (relayed down from inmate to inmate and then back along the dining room table and its row of prisoners, and communicated with the camera acting as if it were the message itself), Cody finally gets the news - he learns that his mother is dead. It is as if a fuse has been lit and the sparks rapidly approach the explosive charge.

[Note: In Each Dawn I Die (1939), Cagney had a kind of 'dress-rehearsal' for this - it contains a similar scene of an hysterical outburst.]

At first disbelieving, the grief-crazed Cody is stunned, furrows his brow and looks down, and whimpers weakly: "Dead?" He privately moans, his body tensing as he attempts to reject the upsetting news. Then, he rises, grips his steel drinking cup, and pounds it on the table - rapidly becoming an uncontrollable, beserk, rampaging lunatic. Cody climbs up on the table, hurtles himself as if swimming down its length, and rolls onto the floor. As a few of the guards grab him, he slugs and punches them right and left, stumbling erratically while making loud, terrible, and inhuman primal cries and sounds. Finally, he is overpowered, brought under control, and carried away - as he flails away kicking and screaming in mid-air like a caught fish. Helpless, he vainly thrusts his body to escape, sobbing: "Gotta get out of here." When order is restored, the men return to the business of eating, and the guards continue to patrol.

In the prison dispensary, Cody has been strait-jacketed and lies on a cot in the barred isolation cell. As Ryley offers him a spoonful of soup, Cody whispers almost inaudibly: "Next time you come, bring the gun." Ryley responds softly: "I'll get it if ya take me along, Cody." Cody agrees: "It's a deal." The prison doctor, Dr. Simpson (Perry Ivins) diagnoses the demented prisoner and recommends commitment in a mental institution: he is "violent, homicidal. He'll probably have recurring periods of normal behavior but...they'll (psychiatrists) commit him to the institution." The Warden of the prison phones Evans to notify him of the latest developments and change in plans - he tells his agents: "No dice, boys. The party's off. Jarrett's a raving maniac. They've got him in a straitjacket...Sorry, boys. They can't all work out."

On a foggy night, Cody is examined by two professional psychiatrists in his isolation cell - he is told that he will be moved "someplace where we might be able to cure your headaches." When Cody's strait-jacket is removed so that he can feed himself now that he is hungry ("Hunger is always a hopeful sign," says one of the psychiatrists), Ryley plants a gun in his hand. When the sleeves of the jacket are peeled off, Cody aims the gun at the guards and psychiatrists, joking: "Examination's over." Ryley knocks out a prison guard, and Cody advises the prison doctor Simpson as he makes a phone call: "And no slips ups, or you're gonna need a doctor." From their cells, Vic, the hard-of-hearing Reader, and Parker are summoned to the dispensary. Parker pleads for his life, fearing that he may be killed in retaliation during the break-out:

Parker: You got me wrong, Cody. I got nothin' against you. It was Big Ed. He told me to do it. You wouldn't kill me in cold blood, would ya?
Cody: No, I'll let ya warm up a little.

Cody's plan of escape runs counter to the one Pardo was expecting (without a firearm), but Pardo can do little to change Cody's determined mind:

Vic: Cody, my way there wouldn't be no shooting.
Cody: There ain't gonna be any 'my way' either. We're goin' out of here in a car like gentlemen on a picnic.

The group of psychiatrists and convicts are led out the ambulance entrance, where Parker is locked in the trunk of the escape car. At gunpoint, Cody threatens the psychiatrists to drive the sedan out of the prison, while the convicts huddle down on the floor (Ryley in the front, and Cody and Pardo in the back) to avoid being detected: "Now you know how jittery I am. Any minute, I'm liable to explode. Now, if we don't make it, I got six slugs in this gun - one for each of us." They are permitted to leave through the prison gate.

In their police car, Evans is notified that "Jarrett's busted out!...Black sedan, probably headed southwest. Following are the names of the men who escaped with Cody Jarrett: Thomas Ryley, Roy Parker, Michael Curtin, Vic Pardo. Do not shoot unless absolutely necessary. Hostages in car."

In a farmhouse of an elderly couple that the fugitives have taken over, Cody wears the dark suit of one of the psychiatrists. He has exchanged places with them - they are tied up and dressed in prison clothes. As he non-chalantly chews on a chicken drumstick/leg while leaving in a second vehicle, he shouts at the sedan's closed trunk: "How ya doin', Parker?" When the victim complains that he is suffocating for lack of air: "It's stuffy in here, I need some air," Cody sarcastically responds, "Oh, stuffy huh? I'll give it a little air," and sadistically shoots four holes in the trunk with his .45 automatic.

In another locale - a lodging house, a radio announcer's voice emerges from a radio. The camera pans around the main room during the broadcast: "No clue to their movements has been reported since their assault last night on a service station north of Gallup, New Mexico. It is assumed now by federal law-enforcement agencies that Jarrett and the other escaped convicts are heading for California. This concludes the nightly news summary from KFKL, San Bernardino."

The camera ends its pan on the nervous figure of Verna, watching Big Ed hammering (with the butt of his gun) a bell next to the front door - a warning device if someone enters. He assures her that he has taken all precautions and will face Cody like a man. On the other hand, Cody's disloyal, selfish wife explains how she must survive by running. She decides to remain, however, when Ed threatens to tell Cody that she was the one who had murdered Ma by shooting her in the back:

Big Ed: Now take it easy, baby. We're ready for him when he comes.
Verna: I can't stand another night, Ed, listenin', goin' crazy. It ain't just like waitin' for some human being who wants to kill ya. Cody ain't human. Fill him full of lead and he'll still come at ya.
Big Ed: Plug him and he drops, same as anybody else.
Verna: The boys didn't think so. Why did they beat it down to San Berdoo?
Big Ed: Because they know this is between me and Cody. They'll be back when it's over.
Verna: You'll be dead.
Big Ed: Maybe so. The time comes when a man's gotta stop runnin' away and face things. Or else go on runnin' for good.
Verna: All right! Throw your life away! Stay here and shoot it out. Me? I'm goin'. I wanta live.
Big Ed: Cody might have some ideas about that.
Verna: I'll go someplace he'll never find me.
Big Ed: The world ain't big enough, sugar, not when he finds out what you did to his Ma.
Verna: (halting, and then startled) You'd tell him?
Big Ed: If you run out on me, why not?
Verna: But I only did it for you, Ed. She had you covered.
Big Ed: Cody still ain't gonna like to hear that she got it in the back. (She stares back at Big Ed, terrified.) Feel more like stayin' now?

In her upstairs bedroom, Verna lies awake stricken with terror in her eyes. The camera captures her as she stealthily descends the stairs, climbs out a side window to avoid opening the door and ringing the alarm bell, and rushes into the garage. There, she is spun around as a hand covers her mouth to silence her scream - it is Cody, ready to half-strangle her for betraying him:

Cody: I said I'd be back. Now tell me you're glad to see me, only say it low so nobody can hear. (He tightly grasps her neck.)
Verna: (struggling) Oh, Cody, I'm so glad to see ya. I been prayin' you'd come back. I couldn't stand it any longer. I was runnin' away.
Cody: From Big Ed?
Verna: Yeah!
Cody: Whatsa matter? Don't ya like him?
Verna: No, no.
Cody: Maybe ya shouldn't've teamed up with him in the first place, huh?
Verna: I couldn't help it, Cody! He said if I didn't go away with him, he'd have ya killed. All I wanted was for you to come back. That's the truth. I love you, Cody, I love you.
Cody: Ya let Ma die!
Verna: No!
Cody: Yeah! Didn't even raise a finger to help her. Just stood there and watched Big Ed kill her.
Verna: I tell ya, ya got it wrong, Cody.
Cody: Maybe ya even thought it was funny. An old woman takin' on a guy like that, huh?
Verna: No. I tried to warn her, but he caught me and beat me. And then when Ma came, he was waitin' for her and he - I, I can't tell ya.
Cody: (fiercely) Tell me...
Verna: He got her in the back.