The Doctor sat up for the eighth night in a row. He hurled his pillow across the room, burying his head in his hands. But he still couldn't get the image out of his head. The image of Amy and Rory, both smiling, before the Angel took them. That image had haunted his dreams. He couldn't remember the last time since the graveyard that he hadn't woken up covered in sweat. After a few minutes of lying down, the Doctor decided he wasn't getting any more sleep. "Oh well" thought the Doctor, "looks like another night wondering the halls."
The Doctor found himself in the control room. "Well, that's odd. I don't remember walking this way" He said to no one in particular. On a whim, he strode towards the doors. He had managed to maneuver the TARDIS into a spot perfect for viewing the Milky Way. With a resigned sigh, he pulled open the TARDIS doors.
Then quickly slammed them shut. It's not possible, he thought. Simply illogical that that was there. "Where the bloody hell are we?" He almost shouted at the console. He grabbed the monitor screen, whipping it around to face him, and was surprised to see the screen completely blank, except for 3 words: YOU ARE NEEDED.
The Doctor cautiously opened the doors again, staring at the wall that had somehow appeared in front of his TARDIS. He stared at the writing on it, until it finally got through to him. Written on the wall in ancient Gallifrayen, the kind the Doctor had seen in books dating back to the building of Gallifray itself, was "TARDIS Docking Bay. Watch Your Step"