In the snowy wastes of blizzard-swept Antarctica, a strange pod-like object is unearthed, buried deep in the ice. Curiosity turns to alarm as the pod begins to grow - then horror when suddenly it cracks open and a snaking green tendril shoots out, mercilessly seeking the nearest live victim...In London, the botanical experts are bewildered. Doctor Who is called in to fight this unknown horror. But will he be in time to save Earth from the rapidly spreading tentacles of the Krynoid, giant man-eating monster from an alien world?