A single old man. One who knows what it is to fight, who understands an enemy few think of any more, who has had to make terrible decisions in his life. And who now, in a museum, with that enemy in front of him reduced to a mere curiosity.
But for the Doctor, Steven and Sara, the landings are anything but random. It's Christmas Day - So many times. What terrible secret is bringing the time travelers to the same day in different years?
The Doctor and Leela arrive on a barren plain in the Soviet Union of the 1950s. Twisted wreckage and remains speak of the tests of a destructive new power. The scientists responsible live in terror of their political masters.