In search of a high-paying job, Claude decides to forgo his life as a law-abiding citizen to become a contract killer. Brinks, an underworld boss, refers Claude to Mr. Moon, one of his underlings, to ask for a job. Moon is at first evasive with the inexperienced killer, but later relents, asks for his phone number and decides to test Claude’s nerves by making him wait two weeks for a call. After Moon gives him his first assignment, Claude proceeds to a barber shop where, posing as a barber, he slits his victim’s throat with a straight razor. For his next job, Claude poses as a doctor, enters the hospital room in which his prey is hooked up to a tube pumping life-sustaining medicine into his body and disconnects the tube. Following Brinks’s orders, Claude, now an accomplished assassin, kills Moon and then travels to Los Angeles to eliminate Billie Williams, a witness scheduled to testify against the gangland boss in an upcoming trial. Claude is met at the train station by Brinks’s henchmen, Marc and George, who are astounded at the killer’s aversion to guns and disinterest in his assignment. Claude, who views murder simply as business, prefers to go sightseeing rather than be apprised of the details of the case. One day, after hitting golf balls at a driving range, Claude insists on attending a movie with Marc and George. After slipping out of the theater and waiting for the others to leave, Claude tails them, and once assured that they are not being followed, asks to be taken to the house in which Billie is being guarded around the clock by the police. Claude is rattled when he discovers that Billie is a woman and demands more money to complete the job because he deems women unpredictable. Posing as an insurance agent, Claude visits Miss Wiley, Billie’s former maid, to question her about her employer’s daily routine. When Miss Wiley tells Claude that Billie is terrified to leave the house and spends her days playing the piano and watching television, Claude rewires the electrical lines into Billie’s house to deliver a high-voltage jolt when she turns on her television set. The next morning, however, Billie uses a remote control to switch on her set, thus avoiding certain death and thwarting Claude’s carefully conceived plan. With only three days remaining before the trial, Marc questions Claude’s abilities and boasts that he could easily kill Billie himself. When the guards are doubled around the house, Claude abandons his aversion to guns and hatches a scheme to draw Billie to the door where she will be within range of a high-powered rifle. After teaching George to use a bow and arrow, Claude sends him into the hills surrounding Billie’s house and instructs him to shoot some flaming arrows at the house, thus starting a fire that will draw out Billie. As Claude waits in the hills with his rifle, a policewoman arrives to guard Billie. When the arrows strike the house, the officer, who was modeling one of Billie’s glamorous peignoirs, runs to the door and is shot by Claude. After Claude reads a newspaper account detailing Billie’s death, he packs his bags and readies to leave town. Before leaving, he phones an escort service to arrange a companion for dinner. When the escort, Mary, arrives, she nervously chatters on and blurts out the Billie is still alive. After getting Mary drunk, Claude asks her where she got her information and she explains that her mother’s uncle, a member of the district attorney’s staff, told her. Certain that the contract is jinxed, Claude refuses to finish the job. George and Marc offer to drive him to Union Station to catch his train, but following Brinks’s orders, detour to a deserted movie studio where they intend to kill Claude. After feigning illness, Claude catches Marc off guard, grabs his gun and pummels him to death with it. Panicked, George runs away, but Claude catches him and kills him with a lead pipe. Claude then phones Brinks, notifies him that his lackeys are dead and demands $10,000 to silence Billie. Proceeding to the Hall of Records, Claude buys a blueprint of Billie’s house and determines that a large drainage pipe runs through the hills and into her basement. That night, Claude wriggles through the pipe and into the house where he knocks the guard unconscious. Telling Billie that he is the new relief man, Claude watches a she sits down at her piano to play a piece of music, then sneaks up in back of her and removes his tie, intending to strangle her with it. He hesitates before he can slip the noose around her neck, however, and she screams, alerting a carload of arriving police officers. When Claude climbs back into the pipe, the officers fire their guns into it, killing him. As Billie picks up the discarded tie, Claude’s bloodied hand slips out of the pipe’s opening.