Dr. Hill's psychic link with other re-animated corpses
I'm just wondering, since Dr. Hill's head had a psychic link with the three (the two male and the policeman's wife) cadavers that "survived" from first movie, didn't he do something with the re-agent in the first movie to allow him to command the bodies he resurrected.
How on earth he could also contact Chapman to get his head from Dr. Graves when contacting the three bodies from the first movie, since Chapman was resurrected by Herbert West, not by Dr. Hill?