This was one of several works Farmer wrote that involved Tarzan.
Plot
The story is presented as a lost manuscript of Watson's, edited by Farmer. On orders from his older brother Mycroft, Sherlock Holmes and Dr. Watson travel to Africa and form an alliance with the titular peer, Lord Greystoke a.k.a. Tarzan, to hunt down the nefarious Von Bork (from "His Last Bow") and stop his deadly new weapon.
