The Tomorrow People

The Vanishing Earth, Part 3 (1x12)

: 23, 1973

Carol and John go back to the Lab and find Stephen, unharmed. The mysterious man reveals himself to be Steen, a galactic policeman, who is chasing the criminal Spidron, who has been raiding planets for magnamite, a rare substance that holds planets together. Steen, Carol, John and Stephen use the matter transporter in the Haunted House to travel to Spidron's base. Spidron releases all his captives from mind control and opens the lava ducts to flood the base.