Wishing to dispose of his wife, psychiatrist Dr. Elliott makes his patient Nina think that she suffers from a compulsion to kill. He drugs Nina, murders his wife and leaves evidence that points to Nina. The latter, pre-conditioned by Elliott, also thinks she is guilty.

Bumbling policeman P.C. Josser is dismissed from the force after a disastrous attempt to distinguish himself at a nightclub. Mistaking his own comrades for criminals, he inadvertently "bowls them over like nine-pins," leading to his immediate firing. After losing his job, Josser sets himself up as a private detective. He is hired by a young lady who owns a racehorse and needs protection for her "favourite" horse before a big race. To protect the animal, Josser goes undercover as a stableman. Despite his efforts, the horse is drugged, leading to further comedic mishaps as he attempts to solve the case and redeem his reputation.

A woman is married to the son of a doctor, the proprietor of a private sanatorium, where she is under unwilling treatment. Both the son and the doctor indicate they want the marriage dissolved. Arriving at the scene is a mysterious personage identified as the doctor's cousin who formerly was a stage magician in Europe. He is accompanied by a threatening dwarf.