On Halloween, Kate Johnson is killed in her bedroom, the victim of a shotgun blast. Her husband Guy is the obvious suspect, having now vanished. In an odd twist, the couple had been part of a television broadcast the previous Halloween where hypnotist Lee Knight demonstrated that people could be induced to do anything, including murder. The deceased's daughter, Katherine Taylor, is convinced that the hypnotic suggestions of a year ago are what caused her father to kill her mother and that Knight is responsible. When she too is found dead, however, the case takes yet another turn. Meanwhile, Dalziel undergoes hypnotherapy to quit smoking.