At an extravagant reception given by his aged Aunt Clementina, Lord Arthur Savile steals a moment alone with his fiancée, Sybil Merton. Finding them, Sybil's mother, Lady Julia, insists that Lord Arthur has his palm read by Mr Podgers, another guest. Lady Julia is relieved when Podgers finds nothing alarming in Lord Arthur's past, but when asked about the future, Podgers' face betrays a look of horror. Composing himself, Podgers predicts a happy marriage and two children, to the satisfaction - tinged with disappointment - of his soon-to-be mother-in-law. But Arthur has spotted Podgers' alarm, and demands to know the truth. Eventually, Podgers agrees to tell more in return for fifty guineas.

Visiting Podgers the next day, Lord Arthur learns the horrifying secret of his future: he is destined to commit a murder, although Podgers is unable to reveal who is to be the victim. Alarmed lest it should interfere with his wedding plans, Lord Arthur resolves that it had best be done before the wedding day.

The next day, Lord Arthur confides his problem in Baines, his butler. After some consideration, they settle on Clementina for the victim, as she is already close to death. Lord Arthur visits an apothecary and procures a capsule of wolfsbane, claiming it is for a rabid Norwegian wolfhound which attacked one of his servants. Returning home, he finds Sybil and her mother. Citing the anticipated death of a near relative, he persuades Lady Julia to postpone the wedding. He conceals the poison capsule in a box of chocolates, which he gives to his Aunt.

However, at Clementina's funeral, Lord Arthur is shocked to find the box of chocolates untouched; he will have to find another victim. At home, where he has a visitor; Herr Winckellhopf spotted Lord Arthur at the apothecary's and recognised in him a fellow anarchist and enthusiast for murder. Lord Arthur explains his lack of ideological intent, but asks Herr Winckelhopf to return the next day. With Baines' help, Lord Arthur selects another victim - his uncle, the Dean of Paddington.

Keen to escape his fate, Arthur revisits Podgers, but meets Lady Julia and Sybil. After he has tried, with little success, to convince Sybil that, despite his desire for a further postponement, he remains committed to the wedding, they leave. Podgers, however, offers no reassurance.

The next day, Herr Winckelhopf is visiting when the Dean arrives unexpectedly. After an unsuccessful attempt to palm the Dean off with Winckelhopf's exploding umbrella, it is resolved to send him an exploding clock, primed to go off at noon the following day. However, the explosion is tiny, and the Dean is unharmed.

Lord Arthur is visited by Lady Julia, anxious to learn of his intentions. An attempt to finish her off by placing a trip wire at the top of the stairs succeeds only in toppling Herr Winckelhopf, who is shaken but unhurt.

Next morning, Lord Arthur has decided to give up and join the French Foreign Legion when hope arrives in the form of a letter from Podgers. But the palmist offers only blackmail - unless Lord Arthur pays him £3000, he will tell the police about the attempted murder of the Dean. At his rendez-vous on the Embankment, Lord Arthur decides instead to throw Podgers into the river.

He returns, relieved and anxious to go ahead with the morning's wedding rehearsal. But the morning paper reveals that Podgers was killed with a dagger; another was responsible. Herr Winckelhopf offers a footstool, rigged to explode after a foot is placed on it. At that moment, Lord Arthur's uncle appears, offering a lift to the church. Offering him the footstool to rest his gout, Lord Arthur attempts to retire to a safe distance, but his uncle has a tale to tell - Mr Podgers was an imposter, a blackmailer, whose predictions were all false, and whose knowledge of his subjects' past was drawn from society records. Lord Arthur manages to dispose of the stool just in time, and, free at last, prepares himself for the wedding rehearsal. But as he leaves, Baines unsuspectingly hands him the exploding umbrella; this time, it goes off. Sybil returns to find Lord Arthur dying in his doorway.