1967. The Australian Outback. The Seventh Doctor, Ace, and Group Captain Gilmore's Counter-Measures team descend on the site of a newly-uncovered alien spacecraft. Amid espionage from multiple sources, the group discovers a mysterious snake-like alien entity when it 'possesses' a politician named Mr. Pendry. . . an entity that kills Pendry when it is forcibly removed. Meanwhile, in 2029, an exceedingly well-preserved Gilmore is rescued from a giant alien spacecraft orbiting the planet. Now returned to Earth, he lifts his long hair to reveal one of the snakelike creatures grafted to his spine. . .
