Thief: The Dark Project is a single player stealth-based game made by Looking Glass Studios for Microsoft Windows PCs and published in 1998 by Eidos Interactive. The player takes the role of Garrett, a master thief plying his trade in an unnamed city. Garrett posesses great thieving and stealth skills, including an almost preternatural ability to hide in shadows. These skills come partly from his growing up as a street urchin and from his later education with the secret society known as The Keepers. The game follows Garrett as he clashes with the powerful and embarks on a journey into the City's strange history, stirring up more than he bargained for.
This is a massive Thief 1 trailer, which was included on the Eidos demo disc at the same time Thief 1 was released. It includes a cinematic made specifically for this video (it was not included in the game) as well as numerous gameplay demonstration clips. It's the best Thief trailer there is.