We open with the title and credits over newspaper headlines and gun images and a jazz score. The opening scene is the Main Street of a small town and George "Machine Gun" Kelly (Charles Bronson) wearing coveralls and a hat. He is carrying a musical instrument case and walking towards a bank. He sees the word "Funeral" in a store window, winces, and turns away to light his cigarette. Anything associated with death or dying upsets him. He enters the back seat of a stolen car driven by two men. The three men drive to the Lebanon bank. They enter and rob the bank. The driver, Maize (Wally Compo) and passenger, Howard (Jack Lambert) assist Kelly with their elaborately planned and timed robbery. They discard their clothes and weapons and the loot is passed to a fourth man, Michael "Fanny" Fandango (Morey Amsterdam). Kelly exits the getaway car and meets up with a waiting Florence "Flo" Becker (Susan Cabot) in her car.
A couple are stopped at a police road block and wait their turn for questioning. Harriet (Mitzi McCall) and Teddy (uncredited) are asked about a car and three men. Harriet is a little confused, and they are allowed on their way. Flo and Kelly drive up and wait for questioning. Flo is cautious but unconcerned. Kelly is angry and resentful and his attitude raises suspicion. A police call informs the roadblock officers that the car they are looking for has been found, abandoned. Before things escalate between Kelly and the police they are sent on their way.
Kelly and Flo stop at a gas station along the road. They chat with an accomplice, Harry (Frank DeKova). Harry has a drinking problem, a character weakness Kelly exploits. Harry collects animals for his roadside zoo. He has a mountain lion he claims he captured himself, with a little help. Harry demands his $200 fee for his part in the robbery, but Kelly is reluctant to pay him. An encounter with Harry's cat convinces him otherwise. Harry gets his money, but also a beating for the way he convinced Kelly to pay. In addition, he gets a healthy scratch from his pet.
The headlines in the local newspaper claim that $41,000 was taken. Flo loves to flirt, because she likes men, and she knows it annoys Kelly. The gang reassembles at a hotel room and waits for Fanny, a nickname Fandango really dislikes, to arrive with the money. When he does finally show he is short about $5,000. Fanny was holding out and they find it in his money belt. At police headquarters, Detectives Clinton (Michael Fox) and Drummond (Larry Thor) meet with a witness to go over mug books. At the hideout, Howard annoys Kelly with a jade figurine of death. He also knows that any mention of death sets Kelly off. The gang is getting a little stir crazy. Flo returns from casing a bank for their next job. Flo informs Kelly that Fandango plans to avenge himself for his rough treatment by Kelly. Kelly meets with Fanny at Harry's gas station. After a brief chat, Kelly pushes Fanny against the mountain lion's cage. His arm is mauled and will be amputated later.
The gang reviews their plans for the bank robbery. An armored car with a large construction payroll delivery is planned, and they intend to intercept it. Flo will block traffic with her car as the others rob the bank. Howard enters the bank and will use a bathroom break as a pretense to get near the vault. Kelly walks towards the bank. The delivery of a coffin to a local funeral parlor spooks him and he retreats unable to complete his part of the robbery. The vault guard notices Howard and a gun fight ensues. The bank manager is killed and the guard chases Howard out of the bank. Kelly finally arrives at the bank but it is too late and he flees. Howard and Maize drive off with Joe (uncredited) and his driver in hot pursuit. They were supposed to pick up the construction payroll. They stopped earlier to assist Flo with her "inoperable" car. In the hail of bullets, one manages to hit Maize and he loses control of the getaway car and crashes. Howard escapes on foot with a non-lethal bullet wound. Kelly and Flo hide out at Flo's mom's house.
Ma Becker (Connie Gilchrist) greets her daughter, Flo, and takes an instant dislike to Kelly. She tells her daughter, "You never could pick your men, could you?" Flo's mom is a Madame and runs a house of prostitution. She has five girls working for her, including Martha (Shirley Falls). Kelly and Flo sit down for a meal and we meet her Dad, Frank (George Archambeault). Frank gives Kelly a drink and talks. When Kelly sees a tattoo of a skull and crossed bones on Frank's hand he immediately shuns Flo's father. Mrs. Becker just loves to needle Kelly and remind her daughter that she isn't a very good judge of men, even crooked ones.
Flo stops at a bar and is noticed by Philip Ashton (Jay Sayer). He was waiting for her, and invites himself to join her at her table for a drink and a chat. He explains that he is, "A friend of Michael's...you call him Fandango, I believe." He informs Flo that Howard blames Kelly for the botched bank job and he intends to kill him. Ashton also informs Flo that Fandango lost his arm. He closes with a warning that Howard and his new gang wants Kelly out of the bank robbery business.
At the house, the girls are entertaining Kelly. Martha has taken a real shine to Kelly. When Flo gets back to the house she expresses her disapproval. She slaps Kelly and gets slapped in return as she is explaining that Howard intends to kill Kelly. Flo reminds Kelly that the botched job was Kelly's fault, but she helps him locate Howard and his new gang. Mrs. Becker continues to needle Kelly after which he visits Howard and his new gang and kills them all while they are playing poker. Kelly decides there isn't enough profit in bank robbery and decides more money can be made with kidnap for ransom.
Flo and Kelly wait in their car outside a school to intercept a little girl. Sheryl Vito (Lori Martin as Dawn Menzer) is the last to exit the school. The kidnappers talk to the little girl while she looks for and waits on her nurse/governess, Lynn Grayson (Barboura Morris) who happens along just as the girl is abducted. Since the ransom note is already being delivered, Flo's suggestion to abandon the plan is overruled. They decide to kidnap both. While Flo escorts the girl into the car, Kelly pulls a gun on Lynn and coerces the nurse into the car. They drive off and meet up with another accomplice, Apple (Richard Devon). All but Flo leave in Apple's car. Flo goes home to pick up clothes and supplies. The gang holes up in a house in the country. Kelly explains the rules to Lynn, and under duress Lynn cooperates fully. A radio broadcast reports Lynn as being an accomplice in the kidnapping, as this was her first day on the job. Also reported is the fact that a ransom note was delivered to Mr. Andrew Vito (Robert Griffin), but no details were released.
Flo arrives with her mom and dad in tow. Kelly is upset, as he doesn't like Flo's parents, but Mrs. Becker explains that, "The child is probably cold, frightened, and hungry, and I'm not leaving until I see that she's all right." Mrs. Becker brings the little girl a doll and reassures the pair they'll be all right if they just do as they are told. Lynn attracts the roving eye of Apple, who pesters her. His untoward sexual attention is deflected by Kelly's intervention with his machine gun. He orders Apple to, "Go outside and look around." Lynn thanks Kelly and is informed she will be a lot of trouble. Mr. Vito's voice comes in on the radio. He is speaking to the gang and tells them he wasn't able to get the phone number to contact them. Flo is sent back to the store to contact her father to make another call to Mr. Vito.
At the local general store the owner is talking to the local policeman, Freddy (Ted Thorpe). Flo walks in to exchange cigarettes she purchased earlier, and to make her phone call. Freddy talks to Flo to inquire about who she is and why she's in the area. Flo asks for a sack of flour to be put in the car. This task gives her a chance to make her phone call unheard. The cop noses around her car, then sees her off. After she drives away, the cop returns to the store to call in. He suspects something and asks the operator about the last call made from the general store phone. He then asks to be connected to the state police to report his findings. When Flo gets back and tells her story about the cop, Kelly gets suspicious and decides to take everyone to Harry's gas station.
The two detectives get a lead on the bar where Flo met with Philip Ashton. They check up on anyone associated with Maize or Howard, now both dead. At the gas station Kelly decides to add Fandango to the caper. He intends to clean up some loose ends and knows given the opportunity Fanny will seek revenge. He wants Fanny to pick up the money from Mr. Vito. Flo and Kelly get into an argument about their life together. Kelly strikes Flo, which brings Apple to her rescue. He knocks Kelly to the floor. Apple asks Flo, "Flo, baby, you want a new man now?" "Sure," is her response. Harry helps Kelly to his feet and gets rebuffed for his trouble. Kelly gives Harry a beating, and as Apple intervenes, Kelly draws his gun on him. The treacherous Flo returns to Kelly, leaving Apple angry, confused and unarmed. Kelly shoots and kills Apple and asks Harry to remove the body. Kelly phones Fandango to engage his services for the ransom pick up. Fanny, now missing his left arm, agrees and leaves the bar. He is picked up and taken to police headquarters. He is questioned, but isn't very cooperative and escapes before he can be followed. A short time later he calls the police to tell them of Kelly's involvement in the kidnapping. Kelly sends Harry to escort Fanny back to the gas station after he collects the money. Kelly doesn't trust Fanny and he is right in his assessment. He informs Flo that he intends to kill his hostages and leave the country with the money.
The police arrange the drop and order the arrest of Flo's parents. Mr. Vito drops the money into a trash barrel and a short time later Fanny picks it up and departs the area. Harry intercepts his quarry and escorts him back to the station at gun point. Kelly awakes on the bottom bed of a bunk bed and images he's in a coffin. He panics and begins screaming and shooting. Fanny makes a run for the door but is stopped by Harry. The police announce they've surrounded the station. Fanny gleefully volunteers that he ratted them out. He eggs Kelly on to shoot it out with the police. That gets him shot and killed by Harry. Harry then shoots at the police and is killed by their marksmen. Flo then confronts the police and threatens to kill the hostages. She is informed her parents are under arrest. His cowardice showing, Kelly thinks he can negotiate with the police to avoid death. Kelly knocks Flo out, blaming her for all his troubles. The police enter and arrest Kelly and Flo and free the hostages. We close with a close up of Kelly's machine gun on a card table.