Gilbert Greenwood and Reginald Seton are bachelors who share a flat on Great Russell Street. Neither are especially prosperous but through economies, they manage to live well. One of their hobbies is fox hunting. One night, Greenwood, on returning from a fox hunt finds a man and a young girl alongside the road. The girl appears to be exhausted and Gilbert offers assistance to the couple . Greenwood learns the man's name is Burton Blair and the girl is Mabel, his young daughter. After some food and rest, Blair relates to Greenwood that he is in search of a secret which will make him wealthy beyond his dreams and that he and his daughter have been searching for that secret for years. As the story unfolds, Burton Blair has, evidently, found his secret and become wealthy although he will share the secret with no one, not even Mabel. One day, returning from a trip, Blair is found dead on a train. The doctors believe it to be a natural death but Greenwood and Mabel suspect foul play meant to obtain the secret of his wealth. An unknown individual has been named to execute Blair's will but no one knows why. A mysterious code is discovered, one which may truly be undecipherable. Could this code hide the secret to his riches? Is Mabel completely innocent as she appeared? And Greenwood is warned that Seton may also not be reputable. Once again Le Queux weaves a tangled web of intrigue and mystery. (Summary by Tom Weiss)