The Master Detective gives us the result of "Some Further Investigations of Christopher Quarles," who seems to be Mr. Brebner's Sherlock Holmes, and who has a Watson of a sort on the detective force of Scotiand Yard. In this connection we must not forget Zena, Professor Quarles's granddaughter, whose "foolish questions" so frequently point to solutions of the various mysteries unravelled by the trio. In the volume fifteen of these mysteries become mysteries no longer when Professor Quarles is through with them. The stories are quite entertaining and their solutions are sufficiently startling to warrant our reading each one to a finish. It is indeed this very quality of unexpectedness that furnishes the ground for the only adverse criticism of the story.