Tobacco millionaire John Vincent Harden has barely arrived in London when strange things start happening to him. The clerk at his hotel swears that Harden has checked out and taken his luggage with him. Then Harden receives a wire calling him home to his plantation in Kentucky - a wire that, it turns out, was never sent. Finally, when a four-wheeled cab almost runs over the American, Harden knows it is time to turn to Sherlock Holmes for help.
Who is behind this peculiar persecution of John Vincent Harden? Holmes solves the puzzle too late, learning in the process that indeed "one may smile, and smile, and be a villain".