Barnaby and Troy investigate an apparent suicide that is just a tad too elaborate for them to accept at face value. The man had been under treatment for depression, his wife had recently divorced him and he owed money to a good many people. Barnaby's doubts are confirmed when the autopsy reveals the man was drugged. There are no end of suspects: the ex-wife, her soon to be new husband who also happens to be a dispensing chemist and the doctor and counselor who treated him at a nearby clinic. When other residents residents of Misomer Worthy are killed, the detectives must try to determine the common link among all of the victims.