London is plagued by a series of police murders, all committed with a sword cane and preceded by taunting notes from the killer, dubbed "X". A diamond thief, Nick Revel, becomes embroiled in the case when a murder occurs outside the location of his latest heist. Despite not being the killer, Nick knows he can't clear his own name until X is caught. He decides to make a deal with the police, using his knowledge to help them catch the real killer while also trying to clear an innocent man, Sir Christopher Marche, who's been wrongly accused. As Nick works with the police, he finds himself falling in love with Jane Frensham, Sir Christopher's fiancé and the daughter of a prominent police commissioner. But with the police closing in on him, Nick realizes he must take matters into his own hands and capture X himself to protect his own reputation and Jane's good name.
The Mystery of Mr. X
A skilled jewel thief, accused of brutally murdering police officers, must utilize his cunning and resourcefulness to unravel the mystery and clear his name.