Sherlock Homes has never been more gruesome. The Testament of Sherlock Holmes, the sixth installment in developer Frogwares’ long-running series of adventures starring Sir Arthur Conan Doyle’s celebrated detective and his sidekick, Watson, kicks off with the discovery of a mutilated corpse. It then proceeds through suicides, another mutilated corpse, poisoned dogs, an autopsy, an opium den, and a generally desolate atmosphere that is a long way from the drawing-room mystery style of this usually all-ages franchise. It might not be the best of the line, given the very high bar set by Sherlock Holmes: The Awakened back in 2006. But the macabre plot, severe characterizations that show Sherlock as an antihero, and lovely graphics combine to make this a mesmerizing adventure.