His name is Deth. He hunts Trancers. Even in the 20th century.
L.A. has been flattened, and then submerged in the 23rd century by the "big one". It's called Angel City now and it's detective Jack Deth's turf. He is a one man elimination squad and Martin Whistler's dehumanized cult goons, the Trancers, are his targets.
When Whistler travels through time to 1985 to eliminate the ancestors of the 23rd century leaders, Deth decides to "take him out" and keep him from unleashing humankind's darkest powers and certain unimaginable chaos and world destruction.