Private Investigator Ed Case returns home after his holiday in Crete is cut short due to his girlfriend Angel being called back on an urgent mission for MI5. Ed has no time to dwell on the disappointment as he picks up an intriguing missing person case. The man Ed is looking for, Owen Moore, has just vanished.
Normally, Ed would ask his friend Detective Inspector Phil Reynolds for help, but Phil is tied up with a murder investigation, looking for a killer who secures his victims to the floor and mutilates them, leaving behind a note "Say thank you John".
Ed runs out of ideas and turns to Data, his friend and computer expert in MI5, for help. Ed finally feels he is closing in on his man when he receives a note warning him off. This has the opposite effect and makes Ed even more determined to find his man; a decision he will ultimately regret.