Intro: The oil rigs of the North Sea have been disappearing. Can the fault lie with a band of over-zealous environmentalists? Don't bet the ranch on it. A more plausible explanation is that it's connected to the "Terror of the Zygons."

Outro: Next week, The Doctor and Sarah, on their way back to London from Loch Ness, will receive a mayday call and will suddenly find themselves on Zeta Minor, a planet on the outer fringes of the known universe. Be with us next Sunday night at 11 for the passage to the "Planet of Evil." [source: ChicagoEpguides]