Based on Mickey Spillane’s novel, detective Mike Hammer investigates a woman’s murder and discovers a trail of murders that lead him to an extremely dangerous secret.
Christina Bailey (Cloris Leachman) stands in the road, and Mike Hammer (Ralph Meeker) stops and picks her up. At a police stop they hear they are looking for a woman in a trench-coat; but he tells police she is his wife, and they let them through. He stops to check a wheel, and a branch is removed. She asks the service attendant to mail a letter for her. She does not give her name and talks about men. He swerves to avoid a car in the road, and a woman’s screaming is heard. Hammer passes out, and men put both of them in the car and push it off the road and down a hill, where the car catches fire.
Hammer wakes up in a hospital bed. He sees Velda (Maxine Cooper), and she kisses him. They leave the hospital, and men from the Interstate Crime Commission question him. Lt. Pat Murphy (Wesley Addy) asks Hammer to tell him what he knows. A mechanic Nick (Nick Dennis) tells Hammer that some tough guys are looking for him.
Hammer enters an apartment and looks around. He has a tape recorder connected to his phone and gets a call from Velda. She comes over, and they kiss. Lt. Murphy comes in and revokes his licenses to investigate and carry a gun. Hammer asks him who Ray Diker is and says he does not know anything. Pat leaves, and Hammer asks Velda to see Diker. She advises him to stay away from the window and leaves.
Hammer goes to Diker’s address at night, and a man starts following him. The man pulls out a knife, but Hammer beats him up and takes the knife. Hammer finds the house and knocks. Ray Diker has a bruised face and tells Hammer where Christina lived. He goes there and helps an old man carry a trunk up stairs. Hammer asks to see her apartment that is being rented. He learns her roommate Lilly Carver moved out. He takes a book and leaves. The old man tells him where the roommate moved.
Hammer knocks, and Lilly Carver (Gaby Rodgers) holds a gun on him as he comes in. He asks her questions. He offers to get even for what happened to Christina and leaves.
At home he hears a phone call about forgetting Christina, and he asks what will happen. He is told to look in front of his apartment. In the morning Nick finds that Hammer has a new car with keys in it. Hammer comes out and warns him not to start it. Nick finds explosives connected to the starter. They get in the car, and Hammer drives to the garage to search the car. Nick finds another bomb. Hammer asks Nick to find out about the car.
Hammer finds Velda exercising to music. He asks her to find out about Christina. She says Ray Diker gave her some names. She says two of them died in traffic accidents. She says Carmen Trevago is an opera singer, and Harvey Wallace drove the truck that killed Kowalsky.
At a family dinner table Harvey Wallace (Strother Martin) says a man was pushed in front of his truck. At a gym Hammer talks to Eddie Yeager (Juano Hernandez), who says his fighter will do well. Hammer asks about Kowalsky, and Eddie says men told him not to talk about Kowalsky if he wants to live. Hammer makes a call and gets the name of Carl Evello.
Hammer goes to a home with a pool and kisses blonde Friday (Marian Carr), whom he never met before. He asks her to invite him into the house, and they drink. By the pool Carl Evello (Paul Stewart) sends Charlie Max (Jack Elam) and Sugar into the dressing-room, where Hammer knocks out Sugar. In the house Carl tells Hammer he is looking for trouble and offers to pay him to go away and then withdraws it.
Hammer goes to Hillcrest Hotel to see Carmen Trevago and finds him singing to a record. He says he knows nothing. Hammer breaks a valuable record to get him to talk about murdered Raimundo. He says they wanted something small he could not hide.
Hammer goes back to Lilly, and she says she hid from them. He takes her in his car to Nick’s garage and says he has to drop something off. After he leaves, a man crushes Nick under a car. Hammer offers Lilly his bedroom, and she kisses him. He tells her not to answer the phone and leaves.
At night Hammer learns that Nick was murdered. He finds Velda asleep in bed and wakes her. She gets up, and they talk. She says Diker pointed her to an art dealer she picked up. He told her about Dr. Soberin. She asks if he wants her to date the doctor.
In a bar Hammer gets drunk on bourbon. The bartender wakes him up and says a man said he got Velda. Hammer drives back to the station and asks about Christina’s letter. He learns it was addressed to him. He goes home and finds the letter that says, “Remember me!” Sugar and Charlie are there with guns. Sugar clubs Hammer. They take him in his car to the beach. Hammer tries to run, and they beat him up. Hammer is tied to a bed. A doctor gives him a shot of sodium pentothal, the truth serum, asking him what he is to remember. Later Carl comes in and asks what she meant by “Remember me,” Hammer only mumbles. Later Hammer gets a hand free and calls to them. Carl comes in, and Hammer calls in Sugar, who stabs tied-up Carl. Charlie hears Hammer’s car drive off.
Hammer goes home, and Lilly lets him in. He has her read from the book he took about “darkness and corruption.” She says they tried to get in. They go to the morgue and look at Christina’s body. Hammer says she must have swallowed it, and the mortician shows him a key. Hammer gives him money. The mortician demands more money, and Hammer slams a drawer on his hand to get the key.
Hammer and Lilly go to the Athletic Club. Hammer goes in and forces a man tell him whose key it is. He learns it was the locker of Nicholas Raimundo. Hammer opens the locker and finds a trunk. He opens it and says it is hot. Bright light shines out. He closes it and the locker. Outside Lilly is gone.
Hammer goes to Lt. Murphy, who demands the key. Hammer says he let Christina and the others get killed. Murphy says Carver’s body was found a week ago. He asks Hammer how his wrist was injured. Murphy mentions the Manhattan Project, Los Alamos, and Trinity, and Hammer hands him the key. Hammer asks about Velda, but Murphy says he can go to hell. Hammer says he did not know. Hammer calls the Athletic Club, where the attendant is dead and the locker is empty.
Hammer goes to Diker and forces him to tell him the name of William Mist. Hammer goes to his art gallery, where Mist is taking sleeping pills. Hammer breaks in and asks where she is, but Mist falls asleep. Hammer finds Dr. Soberin’s name on the prescription. He finds his phone number and calls. A woman answers and suggests his beach house.
Dr. Soberin (Albert Dekker) will not tell Lilly what is in the box because it is evil. He says it is Medusa’s head that turns men to stone. She asks for half. When he refuses, she shoots him. He warns her not to open it and dies. Hammer comes in and asks her where Velda is. She holds a gun on him and asks him to kiss her. As he gets near, she shoots him. She opens the box, sees the light, and screams. Hammer gets up, as the box starts a fire that burns her. Hammer hears Velda and rescues her from a locked room. They go out on the beach as the house burns and explodes.
This classic film noir detective story reflects the tough approach that men have to try to solve problems. The dark secret is the horrendous weapons that have been developed from atomic energy and threaten all life on Earth. This drama indicates that subconscious fear of these weapons and the men who might use them to destroy so much.