On the planet Vortis, the Doctor and his companions aid the butterfly-like Menoptra in their battle against the parasitic Animus and its mind-controlled minions, the ant-like Zarbi.
William Hartnell
The Doctor
Jacqueline Hill
Barbara Wright
William Russell
Ian Chesterton
Maureen O'Brien
Vicki
Catherine Fleming
Animus (voice)
Roslyn de Winter
Vrestin
Arne Gordon
Hrostar
Arthur Blake
Hrhoonda
Jolyon Booth
Hlynia
Jocelyn Birdsall
Martin Jarvis
Hillo
Ian Thompson
Hetra
