Episode Four
Series Episode Number: 286World Premiere: Sat 20 Feb 1971 - 5:15pm BST [BBC One] (United Kingdom)
First Broadcast: Wed 12 Nov 1975 - 6:30pm CST [WTTW 11 Chicago]
Running Time: 24 minutes 40 seconds
7.40 Million (UK)
Chart Position: 63 () (UK)
Recorded on Sat 05 Dec 1970 in Television Centre 8
Archive State: 16mm t/r
The mind parasite within the Keller Machine becomes too powerful for the Master to control. It learns how to move of its own accord and goes on the hunt for new minds.
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