Only hours after his wedding, British international racing driver Alan Colby is injured in an automobile crash. The accident leaves him emotionally disturbed, and during a delayed honeymoon in the south of France, he finds himself attempting to strangle his Italian wife, Denise, whenever they make love. Dr. Prade, a psychiatrist vacationing on the Riviera with his mother, persuades Denise that Alan is in desperate need of help, but Alan scoffs at the idea and returns to London. Prade, now in love with Denise, follows and eventually succeeds in getting Alan to submit to treatment; he uses drugs, autosuggestion, and his own persuasive personality to convince Alan that he has murdered his wife. Panic-stricken, Alan flees to friends on the Riviera. There, one morning, he catches sight of Denise with Prade and confronts them at gunpoint. Prade almost succeeds in convincing Alan that he has hallucinated; but Alan turns the tables on Prade, who himself begins to behave irrationally. Running away, Prade tries to escape by cable car but falls to his death, leaving Alan and Denise free to resume their honeymoon.