The expedition to Zeta Minor began with eight men. Seven were murdered. One survived - but he was not the murderer.
DOCTOR WHO lands on the planet at the same time as the expedition's rescue team, and is immediately taken prisoner - the suspected murderer. But even stranger things soon begin to happen..
What terrible creature inhabits this wild, desolate planet, killing mercilessly, lurking in the murky depths of the Black Pool? Will anyone ever be allowed to leave - alive?