Philip Burton, a wealthy resident of an exclusive Florida island, wakes to a tapping noise. When he goes to investigate, he is confronted by someone identified only as “the beast.” The beast then kills Burton and his wife, leaving behind the business card of Curtis Bird.
The beast next appears in Washington, D.C. Roscoe Bird hears a tapping at his door and answers it to find his childhood friend Peter Tummelier. The reader is led to believe that the beast is Peter, but the identification is ambiguous and remains so at key points in the narration, even though “the beast” is never mentioned again. Peter takes Roscoe out to a bar. While there, Roscoe recalls the suicide of his father, Curtis Bird, caused in part by the Burtons ruining his business. Peter asks if Roscoe wishes the Burtons dead, along with Kate Tornsel, who had contributed to Curtis Bird’s business problems. Roscoe says that he does not hate them that much. Peter, by now drunk, tells Roscoe that he is a vampire. As he leaves Roscoe at his house, he shouts out that he killed the Burtons.
Roscoe soon finds himself implicated in the Burtons’ murders because of his father’s business card found in their house. He believes that Peter is trying to use the murders to persuade him to join in Peter’s plan of leaving everything behind and sailing around the world in a yacht.
Peter continues on his killing spree, murdering one of Roscoe’s enemies along with Kate Tornsel, a policeman, and a woman he picks up in a bar. The murders, told from Peter’s point of view, show that he believes that he is actually a vampire. Marianne, Roscoe’s wife, then disappears. With the help of a police detective friend from Florida, Roscoe finds Richard, Peter’s brother, in an insane asylum. Roscoe does not realize that Marianne is in Richard’s cottage. Richard, however, tells Roscoe where to find Peter. The narration moves rapidly to a climactic confrontation, followed by an epilogue that ties up the story’s loose ends.