Doctor Who: The Tenth Doctor Chronicles: The Thing in the Forest (excerpt)

The Doctor's always loved the Earth. He witnessed its birth and watched it die. It's the home of some of his best friends and even temporarily his as well.

Throughout its history, many alien species have tried to conquer the Earth. Unfortunately for them, the planet is defended and as these invaders are about to learn, the Doctor would do anything to save it.

2.1 The Thing in the Forest by Trevor Baxendale
Norway, 1943. Resistance fighter Ilsa Johansen was sent to locate a British agent. Instead, she stumbles across the Doctor. Pursued through the woods by enemy forces, it'll take all their cunning to survive.

But it isn't just the Nazis that are hunting them. Something else stalks the forest. Something that could change the course of the war forever.