The investigation by Sherlock Holmes of the murder of Admiral Trepoff, a Russian diplomat, takes him to Odessa, where he must match his wits against two opposing factions of the Okhrana – the feared Tsarist secret police. He swiftly discovers wheels within wheels - and the result is shocking to him and to Dr. Watson, who faithfully recorded the case from Holme's account on his return.

This adventure was originally published as a 10-part serial on the Internet.