Thief is an action/adventure game featuring Garrett, an orphan raised by a secretive organization called the Keepers and trained to become a professional burglar. Equipped with a wide range of equipment (lockpicks, blackjack, bombs, a bow and different types of special arrows), Garrett must use stealth and cunning to accomplish the twelve missions of the game.
Thief is a first-person game, using the Dark engine (also used in System Shock 2). Gameplay focuses on stealth: the player is advised to stay in the shadows (the user interface includes a "light gem" indicating how visible the character is), avoid being heard, and avoid guards or find means to distract them. Physical combat is possible but noisy and quite deadly. Mastering the special equipment Garrett uses is an important part of the game, and selling loot between missions to acquire or replenish equipment is crucial.
The game missions are linked by cutscenes that tell the main storyline and describe the world Garrett lives in, as well as flesh out the main character.