Raffles falls in love with the St. Agnes Cup, held in the British Museum Collection, and under threat of imminent purchase by a rich American. Using one of his ingenious disguises and with Bunny's help, Raffles steals the Cup from under the noses of the Security Guards at the Museum. He sends the Cup to Queen Victoria as a Jubilee present on behalf of the criminal element in Society.

Lord Thornaby, head of the famed Criminologists' Club, suspects Raffles of the crime. He invites Raffles and Bunny to a dinner given by the Club at which all members are present at Lord Thornaby's home. Raffles manages to convince them that he really is the Cleverest Cracksman of all time.