In Los Angeles, California, two young men fight with bare fists in a downtown alley until one of them, bounty hunter Zackary Kane, knocks out his rival. Kane—as he prefers to be called—takes the wanted man to the local police station and turns him in to Sgt. Brenner, along with a signed copy of a “civilian arrest” form that lets him claim a reward. When Brenner tells Kane there is no difference between him and the outlaws he brings in, Kane disagrees. Kane returns to his loft, which is filled with homemade art and lined with wanted posters. He marks a large X on the poster of the man he captured. Kane exercises, waiting to go after his next quarry, and relaxes by playing the flute. One night, as Kane comes out of a Pizza Hut, he sees Jennifer Randall, a well-dressed woman, get out of a Cadillac. The driver runs after her, but Kane steps between them and convinces the man to leave. Jennifer thanks Kane, but realizes that the man has driven off with her purse. She walks away, then returns to ask Kane if he wants to invite a lady to dinner? He offers her a piece of pizza. Kane takes Jennifer to his loft for wine and sex. Afterward, she asks him about the art that surrounds them and wonders who he really is, but Kane says very little. Elsewhere, a woman on a dark street is jumped by a man who stabs her with a knife. Though her screams bring people to their windows, no one intervenes. One witness, an African-American woman named Barbara Darrow, recognizes the man. As she packs her bags, she tells her friend, Deke, that she’s “scared to death” and needs to hide because the killer stared at her. The next morning, Kane reads about a $15,000 reward for the murderer in the newspaper. He walks the victim's downtown neighborhood, talking to bail bondsmen, prostitutes and homeless people. When he enters an apartment building near the murder scene, he hears a young woman, Miss Lindsey, being interviewed by two policemen. She tells them her roommate, Barbara Darrow, a singer, was home last night, but packed up and left. Kane goes to the cocktail bar where Barbara performs nightly and takes her photo out of a display case. He visits a noisy bar and finds his African-American friend, Black, playing poker in a back room. Kane tells Black he needs assistance in his search for Barbara Darrow. When Black demands fifty percent of the reward, Kane reluctantly agrees. The men follow a biker named Max Baumer to a gay bar. Kane goes in first and orders a beer. Black follows a minute later. When Kane approaches Max and says he wants to talk to him privately, the biker starts a fight that brings half the patrons into the fray and ends up outside, with Max lying unconscious on the sidewalk. Meanwhile, a man walks into a massage parlor as the woman at the desk, Ginger, is about to lock up. He hands her a $100 bill and she tells him to undress. When she joins him in the massage room, the man, wearing a black mask over half his face, stabs her to death. Afterward, he cries as he caresses her hair. The next morning, Richard Devlin eats breakfast poolside when his servant, Kido, brings him a newspaper and warns that the police will catch him. Richard tells Kido he is not worried because his mother’s wealth and his own quickness will protect him. Richard’s mother, Pamela Devlin, comes out to the patio and sits, wanting to know where her son went last night. Concerned about the lack of improvement in Richard’s behavior, she tells him she plans to ask Dr. Keller to readmit him to the hospital. Determined not to allow her to put him away again, Richard squeezes her hand in a vice grip until she takes back her threat, then he strokes her hair and kisses her on the lips, leaving her shaken. Holding his mother's puffy face in his hand, Richard tells her he knows now why men leave so quickly after they have their way with her. Later, Richard practices martial arts with Kido, who has trained Richard for fifteen years. Now the student has become the better fighter and is ready to deliver a killing blow when he hears his mother’s voice in his head and pulls away. That night, Richard breaks into a woman’s apartment, creeps into the bathroom where she is taking a shower, and pulls back the curtain, ready to stab her. The woman’s male roommate interrupts the scene, and when Richard runs outside, the man follows, but Richard leaves him lying on the ground. Meanwhile, Kane and Black approach a derelict apartment building where Barbara lives under the protection of several African-American thugs. As Black goes up an outside stairway, Kane slips inside, where a man named Ox gets the drop on him. Ox's boss, Efron, first menaces Kane with a switchblade, then Ox and another thug beat him into unconsciousness. Kane wakes up to find Barbara, but she offers no help. Efron just wants him to see her before he dies. As Efron’s thugs drag Kane into the hallway, Black attacks, and the ensuing fight leads them all outside. Black shoots two of the gang, then he and Kane knock out the others. Wiping blood off his face, Black says he has gone far enough for his half of the reward, so Kane is on his own from now on. Kane returns inside to confront Efron and Barbara. When Efron pulls a knife, Kane grabs his hand and drives the blade into Efron's stomach. Kane demands to know the identity of the murderer and Barbara says he is Richard Devlin, a wealthy man she knows from the club. She adds that Efron was going to blackmail him. Kane leaves Barbara on the stairs, crying and alone, then goes to Jennifer’s apartment for a drink. The next afternoon, he awakes after a long sleep and asks Jennifer to use her social connections to get him an entrée to the Devlins. The following night, they go to Pamela Devlin’s lawn party, where Kane notices that Richard keeps glaring at his mother as she kisses and flirts with other men. At one point, Richard sees Jennifer slip inside the house. He follows her, demands to know why she is there, and accuses her of being a "whore" just like his mother. When Jennifer slaps him, Richard changes personality and talks to Jennifer as if she were his mother and he a repentant child. After the party, Kane tells Jennifer to drive home, then sneaks back on the property. As Kane opens a door, Richard knocks him unconscious; Pamela Devlin’s body hangs from the ceiling. Kido drives the unconscious Kane to the beach and carries him to the edge of a cliff, but Kane wakes in time to grab Kido’s pistol and shoot him dead. Jennifer is home, reading in bed, when Richard breaks in. Approaching Jennifer with a knife, he sees an illusion of his mother instead and slashes her. By the time Kane arrives, the police have covered Jennifer's dead body. The next morning, Kane waits in his car outside the Devlin house as Richard leaves on a motorcycle. Kane chases him through streets and into the concrete-lined Los Angeles River, where Richard’s motorcycle gets stuck in the water. Continuing on foot into an adjacent train yard, Kane catches Richard on a railroad bridge, but the killer knocks Kane over the side. Kane grabs a beam underneath, moves hand over hand to the other side, and pulls himself back up. Kane throws Richard off the bridge into the shallow river far below, then walks away.