Tom Conway, a wealthy American from Yonkers, saves a girl from assailants while in London and, with the help of a friend, Tiger Bugg, finds her lodging for the night with Molly Montrose, their actress friend. The following day, Molly discovers that both her jewels and the girl are missing, and Tom supposes that the strange girl, who gave her name as Isabel Francis, is responsible for the theft. Tom later learns that Isabel is the Princess of Lividia, who has run away from her country rather than marry King Danilo (who has also run away and is in London, paying court to Molly Montrose). Danilo and Isabel are kidnapped by agents of Lividia and taken home to be forcibly wed. Tom and Molly follow them, and Tom prevents the marriage.
