When you finish the game, the bad guy escapes and after the credits it says the series will conclude with part 3. Which, unfortunately, was never made.
If I remember correctly, you could see a box with "Manhunter: London" somewhere in the game. Maybe this was to be the title of a sequel that has never been released.
The game was actually Sierra's last to use the AGI game engine that they started way back with King's Quest. A lot of people don't even notice the fact that the game engine is the same, since the interface was so different. (contributed by Jason "Paco" Artman)