Deep Cover, a lost spy game by the makers of Thief and System Shock
 
Deep Cover was a first-person shooter being developed by Looking Glass Technologies and Irrational Games in the 1999 to 2000 period. During the development of System Shock 2, the Looking Glass team began work on a new game which would take the concepts of Thief: The Dark Project into a modern setting. Using the Dark Engine originally developed for Thief, the spy-espionage game took on the title of Deep Cover:  https://www.unseen64.net/2016/04/26/deep-cover-pc-cancelled/