Tony Adams

The Brigadier attempts to seal the giant maggots in the mine with explosives, but this only results in the creatures burrowing to the surface.

In Wales, a dead miner is found glowing green. UNIT investigates and Jo empathises with the environmentalism of Cliff Jones who is opposing the pollution from Global Chemicals.

The Doctor and Jo discover the mine’s terrible secret. Global Chemicals’ managing director, Stevens is determined that they won’t live to reveal what they have learnt.

Investigating the old mine workings, Jo and miner, Bert, become trapped beneath the surface when the lift is sabotaged. Bert touches some green slime and becomes infected.