Jeff is hired simultaneously on two apparently separate cases, one investigating a diamond theft from the company Mortland, the other investigating a haunted house, Merston Manor, for an Estate Agent, Mr. Webster. Realising he can't work on both cases at once, Jeff compiles witness statements from workers at Mortland, while the ghost Marty is sent to investigate the Manor. Jeff in his spare time visits the manor and is scared away by ghostly phenomenon upstairs.
Jeff is summoned alone to a warehouse meeting, whereby he is threatened by the Mortland company Sales Director, Walter Previss, and offered £5000 if he writes the case off as an outside job. Rejecting both bribe and threat, Jeff goes ahead with his plan to expose Previss and is only halted when Previss reveals they've kidnapped Jeannie's sister to ensure his silence.