The third novel in six-time New York Times best-selling author Lois H. Gresh's Sherlock Holmes vs. Cthulhu series.

Both Fitzgerald and Moriarty travel to Innsmouth, the stronghold of the cult of the Old Ones. Holmes and Watson follow them across the ocean and discover a structure designed to enable the Old Ones to flood into our world and unleash horrors that--unless stopped--will annihilate all of humanity. Yet when it is destroyed people continue to mutate and go mad. Cthulhu rises over Devil Reef, ready to unleash his minions. In an epic battle--logic vs. brawn--Holmes must defeat Cthulhu and permanently seal the deadly dimensions.