Thief: Deadly Shadows is a stealth video game where the player takes the role of Garrett, a master thief. It is set in a fantasy/steampunk world resembling a cross between the Late Middle Ages and the Victorian era, with more advanced technologies interspersed.
Thief: Deadly Shadows is a first-person and third-person 'sneaker', similar in gameplay to the previous games in the series. The player takes the role of a Garrett, an independent master thief who aims to steal his way through the City, using stealth, devices and weapons, in order to complete objectives and make profits on the side. The player may steal from or mug innocents for loot, and avoid, distract, attack or knock out guards. Loot and weapon ammunition may be stolen simply by 'touching' it, when close enough. Locked rooms and chests can be broken into after completing a lock-picking minigame. Mission levels may be traversed by sneaking through the shadows, since walking or running will alert nearby guards, who detecting the presence of a vandal will search around for an unknown face. Upon discovering the player, the guards will give chase and possibly hunt him down. In order to make minimum noise, the player must actively monitor the noise each action creates. The player may usually view a hand-drawn map of the immediate surroundings, realistically, the player's location is not indicated on the map and must be deduced from the surrounding landmarks. The game has a fairly open-ended structure, allowing the player to approach every objective in multiple different ways. Upon completion of all objectives, the mission ends and the plot is further revealed through cutscenes.