Ghosts

He's trapped in a book. They're trapped together, in a horcrux formed from a diary. He doesn't know what a horcrux is, but he knows that there's not supposed to be two Tom Riddle's in it. / In which two bits of soul end up in the diary, Lucius Malfoy leaves it in a muggleborn's books instead, and Colin Creevey gains a friend who is bad for him.