Wales, the near future. While the Doctor finally gets to visit Metebelis Three, Jo and UNIT investigate a spate of strange deaths near Global Chemicals' plant. What effect has the company's toxic waste had on the local wildlife?
The Doctor and Jo discover the mine’s terrible secret. But a giant maggot hatched from an egg that the Doctor brought back from the mine is on the loose.
Cliff and the Doctor work to find a way to destroy the green maggots. Time is running out as they emerge from the mine to menace the entire area.
