In the week before private detective Marty Hopkirk's wedding to waitress Jeannie Hurst, he and his partner, Jeff Randall, get a job from famous artist Gordon Stylus to watch over his wife, as he fears for her safety. In the course of the assignment, Marty is killed, and the grieving Jeff and Jeannie must investigate how he died, which then endangers their lives. Fortunately Jeff begins to get help from Marty's ghost, which only he can see. Marty fails to get back to his grave in time and is cursed to walk the earth for the duration of Jeff Randall's life, visible only to him...

Jeannie joins the private detective agency, and investigates the repeated disappearance of money from the till of a local casino. Meanwhile, Jeff goes to a private psychiatric clinic run by Dr Lawyer, to try to get over Marty's death and rid himself of the ghostly apparitions. Marty gets tutorials in being a ghost and doing impersonations from his mentor Wyvern. After Jeannie solves the case at the casino, the detective agency's offices are broken into, and the trail leads Jeannie back to Jeff at the clinic.

When Jeannie senses that her nephew, Daniel, is unhappy at his boarding school, she quizzes him about it, and he lets on that he thinks a teacher was murdered. Jeff and Jeannie get jobs there as teacher and nurse, to investigate, and find that the headteacher is exerting a sinister influence on the boys.

Harry Wallis was once the partner in the police force of Marty's father, Larry Hopkirk, until Maurice Crabbe killed Larry and disabled Wallis, in revenge for their killing of his brother, the hardened criminal Sidney Crabbe, though Maurice is also left severely disabled by the incident. Marty's tuition from Wyvern concludes, and he is then able to enter Limbo, but there he realises that its attractions are only superficial. Now that Wallis is approaching the end of his life, to salve his remorse he hires Jeff and Jeannie to locate Maurice Crabbe so that he can give him some of his savings to pay for his care.

The enigmatically beautiful Lauren Dee hires Jeff to investigate the disappearance of her husband somewhere in rural England, but it proves to be just a ploy to entice Jeff and Marty into the grip of a village that Time has bypassed since the Middle Ages. Wyvern realises that the only way to save Marty is to enlist the help of Jeannie.