A true descent into hell starts for Sherlock Holmes when London begins to have doubts and starts to lose its trust in him who is incapable of refuting suspicions or of disproving the charges against him. Even Doctor Watson's unshakable faith in his friend starts to waver as the famous detective avoids Scotland Yard, started making strange behaviors like night escapades, blackmail, and destruction of evidence, and raises further suspicions.
The main premise of The Testament of Sherlock Holmes comes in the desire of the Frogwares development team to truly explore Holmes as a character. In previous games as in Sir Arthur Conan Doyle's books, the cases were always about truly devious criminals. In this game, as players get further into the storyline, it startsshowing Watson's own point of view and investigation that Holmes takes increasingly darker approaches to solving crimes, up to a point where he commits murder.