The Tomorrow People

The Vanishing Earth, Part 4 (1x13)

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Ginge breaks free and closes the lava ducts, while Steen, Carol, John and Stephen find the Spidron's control room, just as he and Joy teleport away. Later, Joy goes to Spidron's hideout near his spaceship, and they prepare to leave Earth with the magnamite. Steen, Carol, John and Stephen track Spidron's spaceship to London, where they find a sewer entrance. Spidron uses mind control on Ginge and Lefty, and escapes alone in his spaceship. Steen arrests Joy, who reveals that she double-crossed Spidron by keeping the magnamite on Earth in the mining areas. When the lava reached the storage areas, the magnamite flowed back into the Earth's crust, stabilising it and averting the destruction of the planet.