Behind the fourth door is a new story, called Number 1, Gallows Gate Road. It is part 1 of the story, and so there will be at least one following part in the future. It is written by Rupert Laight, and the illustrations for the story are by Brian Williamson. Below is a snippet of the story.
The Doctor was standing in a small attic bedroom with a low, sloped ceiling and peeling, yellowed wallpaper. It was furnished simply with a narrow single bed and a chest of drawers, on top of which were his clothes, neatly folded.
He turned back to the dust-covered window and saw what had been making the tapping sound. The uppermost branches of a tall oak tree were scratching against the pane.
Got to find out what's going on, thought the Doctor, and he pulled on his clothes and flung open the bedroom door.
'Hello, Doctor,' said a voice on the brink of breaking. 'Did you sleep well?'
You can view it in full here.