Crossover Cover: Locked Rooms

Sherlock Holmes and Mary Russell are in San Francisco, where they cross paths with writer Dashiell Hammett, who tells Mary her former psychiatrist was murdered using “some kind of bird carving…an owl maybe, from Rhodes or Crete or something in the Mediterranean.” The statue used to murder Russell’s psychiatrist will later become the subject of a book by Hammett entitled The Maltese Falcon.

Crossover Cover: A Letter of Mary

In this novel, Mary Russell Holmes, Sherlock's much-younger wife and apprentice, is helped out of a spot of trouble by a young monocled man named Peter. As the acknowledgments for the book state, this is Dorothy L. Sayers' sleuth Lord Peter Wimsey, who according to Farmer is a Wold Newton Family member and a distant cousin of Sherlock Holmes himself.

Crossover Cover: The Game

In this novel, Sherlock Holmes and his much younger wife and apprentice, Mary Russell Holmes, are assigned by Sherlock's brother Mycroft to travel to India to search for the missing British agent Kimball O'Hara. O'Hara is the title character of Rudyard Kipling's novel Kim. (As a side note, according to Kipling, Kim's father was a member of a fictional Irish regiment in Afghanistan called the Mavericks. Another Kipling story, "The Mutiny of the Mavericks," describes an Irish revolutionary's ultimately unsuccessful attempt to stir the regiment into mutinying. Therefore, "The Mutiny of the Mavericks" will be in the new volumes.)