A suave thief falls in love again with his high school sweetheart and finds temptation and a detective on his trail while visiting her family.

Unknown to Scotland Yard, the thief operating under the sobriquet of "The Amateur Cracksman" is actually A. J. Raffles, a cricket star and English gentleman who steals to support his elegant life style. When Raffles falls in love with Gwen Manders, he renounces his life of crime, but this does not deter Scotland Yard's Inspector MacKenzie from his investigation. Raffles' reformation is short-lived, however, as Gwen's brother Bunny confides that he desperately needs £1,000 in order to repay the money he embezzled and lost at gambling. An empty cigarette package, meanwhile, leads MacKenzie to the country estate of Lord Melrose, where Raffles is weekending. However, it is not the inspector but Raffles who discovers the plot of petty thief Crawshay to steal Lady Melrose's emerald necklace. Raffles wrestles the necklace from Crawshay, who is then arrested by the police. The next morning, Raffles leaves for London to sell the jewels, and Gwen overhears the inspector setting a trap for him. She rushes to warn Raffles, but too late, for the inspector springs his trap and arrests Raffles with the gems. Raffles exhibits his ingenuity one last time as he cleverly eludes the police and escapes into the night.