Blakes 7 S03 E10 Ultraworld

The Liberator detects a mysterious spiky metal globe floating in space. Avon deduces that it is an artificial planet, but can't raise any communication. Then Cally disappears - apparently abducted inside the "planet". As well as affecting minds, this "Ultraworld" turns out to be capable of stealing them - and using the zombified bodies of space travelers to trap others. But the crew must ultimately face the menace that rules from the center of the Ultraworld... Original Broadcast Date, 10th March 1980.