What does a list of seemingly random initials carved into a tree have to do with the Doctor? And, more importantly, what does it have to do with Clara?

Hiccup Haddock sat bolt upright in an unfamiliar bed, in an unfamiliar place with three unfamiliar faces staring back at him. Welcome to Tower Prep! When Hiccup finds out where he is, his first thought is of escape. He will need to enlist the help of an exciting ice specialist, a brave archer, a caring princess and a motherly computer system called Valka119

Two completely different people become friends in an unlikely situation. The people? A skinny nerd called Hiccup and a popular jock called Jack. The unlikely situation? A zombie apocalypse.