The story is that of the mysterious murder of John Argyle, a multi-millionaire, in the library of his home. Circumstances point toward Argyle's adopted daughter Mary, who is the beneficiary under his will, Argyle having quarreled with his son Bruce. Just as the case begins to look black for Mary, Asche Kayton, a great private detective, is called in by Bruce and takes hold of the investigation. His methods are scientific and swift and the trail leads to a den of counterfeiters, where, by use of the dictograph and other modern devices, the real murderer is run to his lair. Kayton falls in love with Mary, who is finally vindicated. Kayton's reward is the girl.