In this text adventure the player controls Dr. Watson, exploring familiar locations in London, questioning suspects and solving puzzles. The interaction with the game world is performed by typing combinations of verbs and objects. Descriptions of locations must be read carefully, as they may contain clues vital to solving the game.

You have received an urgent summons to the rooms of your good friend Sherlock Holmes by his landlady, Mrs. Hudson. Normally you are not up and about so early on a Saturday. But here you are, outside the Baker Street residence, and not a moment too soon, for the fog has thickened and travel without a lamp has become impossible.