In a future London suffering from toxic air pollution, a reporter, his mentor, a weatherman and an environmental activist discover they are connected and set out to expose the corrupt Airzone Corporation.
Former UNIT luminary Liz Shaw and her assistant Lou Bayliss are investigating a series of bizarre murders, all committed near a soon-to-be-closed psychiatric hospital. When the hospital is unexpectedly reprieved by rich Industrialist Peter Russell events seem to move out of Liz's control. Are the incumbent director of the clinic, Doctor Dove and his predecessor Doctor O'Kane harbouring the killer? What is the centuries-old horror hidden in the grounds? And what exactly is the secret of room zero?
When P.R.O.B.E. is summoned to investigate the savage murder of a retired headmaster, Liz Shaw is disturbed to find evidence of satanic rite near the scene of the crime. She soon discovers a web of deceit and corruption that extends back in time, threatening the current occupants of nearby Winterborne School. With P.R.O.B.E. under threat from within and the death toll mounting, Liz finds herself under increasing pressure from all sides to produce results... The Devil of Winterborne is at large and only Liz can stop it!
In 1975, the British Government quietly closed down a secret evolutionary project codenamed BEAGLE, ordering the destruction of all research materials. Today, the discovery of several horrifically mutated bodies alerts Liz Shaw and P.R.O.B.E. to the fact that something is stalking the original site of project BEAGLE - something which may challenge the very nature of humanity itself! With a crack security team at her disposal, Liz desperately attempts to track down the perverted results of the project. But who or what is hunting whom?
The Devil of Winterborne has only recently been exorcised by P.R.O.B.E. But when the body of its last victim disappears, and a book of black magic spells is stolen from a local museum, Liz Shaw begins to wonder if the ghosts of the past have really been laid to rest. Forced into an unholy alliance with the school's disgraced headmaster, Liz must fight not only her own warring emotions, but a festering evil that threatens to corrupt the Earth again after 100 years.
Liz investigates the government execution of an immortal Corporal who 'no longer has a use'.
Giles talks to the camera about his fears and doubts because a reservoir of evil is returning at the next perihelion...