Per Wikipedia: it is set in the (then) futuristic year of 2004, when Earth has been enslaved by a race of aliens known as the Orbs. The Orbs, who look like giant floating eyeballs, have implanted all humans with global tracking devices, forced them to wear nondescript robes and forbid them from speaking or communicating. The protagonist has been assigned by the Orbs to track down fellow humans who are believed to be forming an underground resistance. Over the course of the game, the player discovers that the Orbs are not the benevolent rulers they claim to be; they are actually harvesting humans as a food source. The player then "switches sides" and works to overthrow the Orbs.

Gameplay
Manhunter: New York used Sierra's Adventure Game Interpreter (AGI) development tool. It was very different from other AGI games in that it did not use a text parser, incorporated a first-person rather than third-person perspective, and featured a rudimentary point-and-click interface. The gritty, sometimes gory visuals, unique interface, and use of real-life locations in New York City all helped set the game apart from Sierra's other titles, which were typically more family oriented.