Captain Munsey, the prison captain of the Westgate Penitentiary, is despised by inmates and prison officials alike for his brutal treatment of the inmates. While Munsey's enemies include prison doctor Walters and Warden Barnes, he is supported by some inmate stool pigeons. One of the stool pigeons, Wilson, is killed when a group of prisoners force him into the workshop steel press. As living conditions at the prison continue to deteriorate, some of the inmates, including leader Joe Collins, who landed in prison for stealing money to support his wheelchair-bound wife, Spencer, Tom Lister and Soldier, plan a breakout. A painting of a woman hanging on one of the prison's walls prompts each of Joe's pals to recall his sweetheart, and the specific circumstances that led up to his imprisonment. Spencer remembers every detail about the day he was framed by his sweetheart, Flossie: When an illegal casino in Miami is raided, Flossie helps Spencer escape through a rear exit. She takes Spencer's gun under the pretext of protecting him, but then holds him up, steals all his money, forces him out of his car and drives off, never to be seen again. It is Spencer, not Flossie, however, who is eventually captured by police and sent to prison. Next, Tom tells his tale of woe: One day, he presents his beloved wife Cora with a three-thousand dollar fur coat, but admits that he feels guilty about having juggled the books at his job to pay for it. Cora cares little about Tom's worries and is only concerned about keeping her new coat. Even after being imprisoned for embezzeling, Tom still eagerly awaits Cora's letters. Soon after Spencer and Tom conclude their stories, Tom is pressured by Munsey to inform on his fellow inmates. When Tom refuses to cooperate, Munsey devastates him by lying that Cora is divorcing him, and as a result Tom hangs himself in his cell. When the suicide is discovered, Munsey accuses the cellmates of murder and punishes them with backbreaking work in the prison drainpipe. While they work, Soldier tells his pals about the fateful day when he took a murder rap for his beloved: After completing his tour of duty during World War II, Soldier returns to a small Italian town to resume his romance with his sweetheart Gina. Gina's father, however, disapproves of their romance, and when he threatens to report Soldier to the military police, Gina shoots him, and Soldier takes the blame. As the men continue to work, Dr. Walters accuses Munsey of torturing the prisoners, causing Munsey to become enraged and strike the doctor. At the same time, the men plan to escape through the drainpipe, but only hours before the breakout, Munsey begins to suspect them and denies one of the prisoners, Louie, a special pass to enter the pipe area. Munsey then tortures Louie in an attempt to wring a confession from him. Joe soon discovers that Louie was tortured and that one of his fellow inmates tipped off Munsey. Joe decides to test his pals to determine who the informant is, and eventually comes to suspect an inmate known as Freshman. Joe's suspicions are confirmed when Freshman violently objects to being the first to enter the drainpipe. Instructed by Munsey to shoot to kill anyone attempting an escape, the guards kill Freshman as he emerges from the drainpipe. When Joe and the others try to sneak past the guards, a gun battle erupts during which Joe kills Munsey. Joe himself is soon shot, but manages to open the prison gate before he dies. The prisoners' escape appears assured until Gallagher, the getaway truck driver, is killed and the guards capture or kill the rest of the inmates. Surveying the bloody scene, Dr. Walters wonders out loud why the men attempted such a foolish escape, saying, "Nobody escapes. Nobody ever escapes."