On a rainy night in 1928 in a Pennsylvania factory town called Iverstown, Martha Ivers (Janis Wilson), thirteen years old, is trying to escape from the guardianship of her wealthy, domineering aunt. Her friend, the street-smart, poor Sam Masterson (Darryl Hickman), comes for her through her bedroom window, but Martha's aunt catches them. While Sam slips out unnoticed, Martha hits Mrs. Ivers on the head, causing her to fall down the long staircase and die. Though Sam saw nothing, the event was witnessed by Walter O'Neil (Mickey Kuhn), the son of Martha's tutor (Roman Bohnen), known as Mr. O'Neil. Martha lies about the incident to Mr. O'Neil, and Walter supports her.
Christopher "Chris" Cross (Edward G. Robinson), a meek amateur painter and cashier for clothing retailer, J.J. Hogarth & Company, is fêted by his employer, honoring him for twenty-five years of dull, repetitive service. Hogarth presents him with a watch and kind words, then leaves getting into a car with a beautiful young blonde. Walking home through Greenwich Village, Chris muses to an associate, "I wonder what it's like to be loved by a young girl." He helps Kitty (Joan Bennett), an amoral fast-talking femme fatale, apparently being attacked by a man, stunning the assailant with his umbrella. Chris is unaware that the attacker was Johnny (Dan Duryea), Kitty's brutish boyfriend, and sees her safely to her apartment building. Out of gratitude and bemusement, she accepts his offer for a cup of coffee at a nearby bar. From Chris's comments about art, Kitty believes him to be a wealthy painter.
In Bangor, Maine in 1824, a cruel young girl named Jenny Hager pushes a terrified Ephraim Poster into a river knowing he cannot swim. She is prepared to let him drown until Judge Saladine happens by, at which point Jenny jumps into the water and takes credit for saving the boy's life.
Navy pilot Lieutenant Commander Johnny Morrison (Alan Ladd) is put on the inactive list. He returns home to Hollywood from the fighting in the south Pacific, bringing along his buddies and medically discharged crewmates Buzz Wanchek (William Bendix) and George Copeland (Hugh Beaumont). Buzz is prone to memory lapses and headaches, and is often short tempered, all likely due to his head wound.
Sandra Marshall (Barbara Stanwyck), the widow of the owner of a remote mansion, arrives to take charge and claim the inheritance of her late husband. She receives a cold reception, especially from research scientist Mark Caldwell (Errol Flynn), who seems to be keeping her sister-in-law Julie (Geraldine Brooks) a virtual prisoner in the house.
Ex-boxer Kevin "Kid" Collins is a drifter and an escapee from a mental hospital. In a desert town near Palm Springs he meets Fay Anderson, a widow, who convinces him to help fix up the neglected estate her ex-husband left. She nicknames him "Collie" and lets him sleep in a trailer out back, near her dying date palms.
Tired of the low pay of his profession, hard-boiled private detective Phillip Marlowe (Robert Montgomery) submits a murder story to Kingsby Publications. He is invited to the publishers’ offices to discuss his work but soon realizes it is merely a ploy. On Christmas Eve, publishing executive Adrienne Fromsett (Audrey Totter) hires him to locate the wife of her boss, Derace Kingsby (Leon Ames).
Steven Kenet catches his unfaithful wife in the apartment of Willard I. Whitcombe, her boss, and apparently strangles her. Believing he killed her, he attempts to commit suicide by driving his car into the river, even though they have a 6-year-old son. Kenet survives but is sent to the county psychiatric hospital for evaluation to determine if he is sane enough to be charged with murder. He has no memory of what happened, likely due to a pre-existing brain injury from the war.
Johnny Eager (Robert Taylor) masquerades as a taxi driver for his gullible parole officer, A. J. Verne (Henry O'Neill), but in reality, he is the ruthless head of a powerful gambling syndicate. Verne introduces him to socialite Lisbeth "Liz" Bard (Lana Turner), a sociology student. Johnny and Liz are attracted to each other, but then he discovers that she is the stepdaughter of his longtime nemesis, John Benson Farrell (Edward Arnold). As a crusading prosecutor, Farrell was responsible for sending Johnny to prison, and now as the district attorney, he has gotten an injunction preventing Johnny's expensive dog racing track from opening.
Walter Neff (Fred MacMurray), a successful insurance salesman, returns to his office building in downtown Los Angeles late one night. Visibly in pain, he begins dictating a confession into a Dictaphone for his friend and colleague, Barton Keyes (Edward G. Robinson), a brilliant claims adjuster. The story, told primarily in flashback, ensues.
Manhattan press agent Sidney Falco (Tony Curtis) has been unable to gain mentions for his in J.J. Hunsecker's (Burt Lancaster) influential, nationally syndicated newspaper column of late because of Falco's failure to make good on a promise to break up the romance between Hunsecker's younger sister Susan (Susan Harrison) and musician Steve Dallas (Martin Milner), an up-and-coming jazz guitarist.
Glenn Griffin (Humphrey Bogart) is the leader of a trio of escaped convicts who invade the Hilliard family's suburban home in Indianapolis and hold four members of the family hostage. There they await the arrival of a package from Griffin's girlfriend, that contains funds to aid the three fugitives in their escape.
In 1935, French Diplomat David Talbot (William Powell) and his bride Lucienne (Hedy Lamarr) are enjoying their third month of marriage in Paris when Talbot is confronted by extortionist Carlos Le Duc (Vladimir Sokoloff) who demands money in exchange for not turning him in to the police.
Christine Radcliffe (Bette Davis) runs up the stairs of a college concert hall in the rain. The hall is filled with enraptured students, and her eyes fill with tears as she recognizes the cellist on stage: Karel Novak (Paul Henreid) who spent the war trapped in neutral Sweden. After the performance, Novak is mobbed by well-wishers, and a student reporter questions him about his favorite composers. Novak lists some famous ones, then adds, "And, of course, Hollenius."
On the U.S.-Mexico border, a time bomb is planted in a car. A man and woman enter the vehicle and make a slow journey through town to the U.S. border, the woman (Joi Lansing) insisting that she hears something ticking. Newlyweds Miguel "Mike" Vargas (Charlton Heston), a drug enforcement official in the Mexican government, and Susie (Janet Leigh) pass the car several times on foot. The car crosses the border, then explodes, killing the occupants. (The cut to the exploding car is the first one in the film, the single-camera opening sequence lasting nearly three and one-half minutes.)