When scientists in the Antarctic uncover a mysterious seed pod, the Doctor is called in to investigate. He soon realises it is extraterrestrial and extremely dangerous. At the same time, however, ruthless millionaire plant-lover Harrison Chase has learned of the find and decides he must have the pod for his collection of rare and beautiful flora. Meanwhile the pod itself harbours intelligent life with sinister plans of its own...
Tom Baker
The Doctor
Elisabeth Sladen
Sarah Jane Smith
Tony Beckley
Harrison Chase
Kenneth Gilbert
Richard Dunbar
Michael Barrington
Sir Colin Thackeray
Sylvia Coleridge
Amelia Ducat
John Challis
Scorby
Mark Jones
Arnold Keeler / Krynoid (voice)
