A juvenile ghost haunts the mountain-pitched castle overlooking sleepy medieval German town Eulenburg ('owl burgh'), one hour after every midnight for centuries, without aging or interacting with people as it's closed at night. However repairs at the clock tower result in the ghost becoming visible, black and active all day. Shy schoolboy Karl gets in trouble for telling the truth as nobody believes the antique watch that disappeared from the castle during his class's visit was stolen by a ghost, so he's the prime suspect. Many town-folk get scary meetings before the case is cleared and the ghost's condition normalized through the clock that upset him.