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?