I don’t understand it. He just seems to be worn out.
As Doctor Who stories go, quite a lot is asked of Kit Pedler’s “The Tenth Planet” (Story Production Code DD). In addition to delivering a ripping near-future yarn about cybernetic invaders from a twin-Earth, the story also needed to usher out William Hartnell’s First Doctor in a fitting and dignified manner. Pedler, with assistance from story editor Gerry Davis, manages both with some aplomb. Not only do we get the Cybermen, more frightening here in their debut story than in any future iteration, but also, Hartnell is given the chance for the virtuoso exit he richly deserved.
The TARDIS again finds its way to Earth, skipping from seventeenth century Cornwall to twentieth century Antarctica, though in 1986, twenty years in the future from Ben and Polly’s time, much to their dismay. With plenty of warm coats in the TARDIS wardrobe to choose from, our time travellers merrily pop out onto the ice cap for a visit, only to be apprehended by soldiers from the International Space Command, at whose polar base the TARDIS had landed. The commanding officer, General Cutler, has no time to interrogate his guests, however, as a space capsule on a routine mission has run into trouble. Some outside force is pulling the astronauts from their planned orbit. And the Doctor knows just what has happened.
In order to prove his knowledge of events, and thus potentially to help, the Doctor gives a scientist at the base a piece of paper noting that the problem stems from the sudden appearance of another planet—the Tenth Planet—in Earth’s vicinity; and not just any planet, but Earth’s long-lost twin, Mondas, with the same continents (and continental drift), only upside down. What’s more, the Doctor knows that Earth is about to receive visitors.
The Cybermen are on their way. They don’t want much, really. Just to drain the Earth of all of its energy and then destroy it.