When philosophy professor Henry Todhunter learns he has only six months to live, he polls the members of the University Club to learn what they would do in a similar situation. Each man has a different answer, but Henry's interest is piqued when one suggests murdering a person who is a menace to society. Henry discusses the idea with his doctor, Lawrence Stevens. Although Larry argues that no man is entitled to act as judge and jury, Henry believes that a man facing death possesses the immortality to act without self interest for the benefit of society as a whole. Henry's friend, Betty Farroway, who is waiting for him when he returns home, is concerned because her husband Michael, an artist, is acting strangely. Henry agrees to talk to Michael and accompanies Betty home in a taxi. Stuck in traffic, Henry and Betty see Michael kiss Ketti Moret in front of her gallery. The next day, Henry asks Ketti to stop interfering with Michael's life, and she replies that her only interest is in his work. Later Michael is hit by a car and while semi-conscious begs Betty to destroy a painting. Intrigued, Henry and Betty explore Michael's studio, where they find a painting done in the style of an ancient painter. Henry realizes that Michael has been forging paintings for Ketti, and believing that in Ketti he has met a truly evil person, investigates her life. He learns that no one, not even her abandoned child, her mother, or her former husband cares if Ketti lives or dies. Michael admits painting the fakes and Henry suggests that he ask Ketti to reveal the real painter to the person who bought the counterfeit painting. When she refuses, Michael threatens to kill her and is overheard by Ketti's maid. After Michael leaves, Henry emerges from his hiding place in Ketti's apartment and kills the unremorseful woman. Henry's plans go awry when Michael is arrested for the murder. Henry immediately confesses, but at first, no one believes his story. Eventually, he convinces Larry to testify to their conversation on the subject of murder, and is soon convicted and sentenced to death. Henry plans to exert himself enough to cause a fatal heart attack and thus avoid the electric chair, but when one of his former students is brought to jail after having been inspired to murder by Henry's example, he realizes the damage that he has done and accepts his punishment as just.