They were all walking along the tunnel, Hagrid barely fitting through and were all proceeding to the Gryffindor common room. They were running, but quietly enough that they did not disturb the sleeping students. Harry flung the bookcase door open but stopped dead in his tracks. Standing in front of him was Professor McGonagall, with a stern look on her face.
"What are you doing running about at this time in the morning Potter? And exploring secret passages are we?" McGonagall glanced at the Doctor and River. "You brought friends too i see." The Doctor pushed his way forward and extended a hand to the professor.
"Hi, I'm the Doctor, this is River Song," McGonagall did not shake his hand, so he moved it to his side. "I really do sincerely apologise but I crash landed in your school and I will be gone soon."
"You're getting rid of the alien first!" Ron shouted from a bit further down the tunnel. Hagrid had disappeared, he had obviously retreated when he saw the professor.
"Alien?" McGonagall looked skeptical but angry. "Potter, Weasley, explain please?"
"I'm sure we can do that once we've killed the alien," the Doctor said. "We only have..."
"23 minutes," Hermione interjected.
"23 minutes until your students wake up and find an alien in the corridors and the likelihood is, when they find the slitheen it will kill them."
"And how do you intend on killing this monster," McGonagall asked.
"Vinegar," Harry said, in all seriousness. McGonagall laughed, then realised he wasn't joking. She looked up at the Doctor.
"Very well, do you know where this alien is?" She looked at the Doctor expectantly. His face was blank and he bit his lip nervously. "You don't know where your murderous alien is!?" She cried.
"Not quite, it's highly likely it's still in the school, well, maybe not highly likely, probable at the most. If we want any chance of catching it we need to go now." McGonagall moved out of the way and the group of them started walking towards the common room door, the Doctor led the way, with River and McGonagall at his heels, while the three young wizards trailed behind whispering.
"Bloody hell." Ron uttered. "Of all the crazy things we've done, this has to be the craziest."