A spate of armed robberies lead the CID unit to prison, to escort notorious safe-cracker Dickie Fingers for interview back at the station. However, as they transport him they are set upon by a dangerous gang determined to get their hands on Fingers.

When the body of a young woman is found in wasteland, DCI Gene Hunt fears a serial killer he thought he'd sent down in the late '60s may still be at large. For Sam, the victim, a Beauvoir beauty rep like his own Aunt Heather, triggers vivid recollections of his childhood.

Utilising his knowledge of modern surveillance techniques, Sam is led to middle class suburbia where a local car dealer, Roger Twilling, is throwing private parties employing the poorly paid make-up girls to help out when the lights go down and the wife-swapping begins.

Sam and Annie go undercover as a young swinging couple to infiltrate the world of vol-au-vents, Blue Nun and lava lamps. Never one to miss out on the fun, Gene Hunt storms in uninvited with a female 'friend' posing as his other half.