Moomintroll's mind starts to play tricks on him when he's left home alone over night for the first time. But his worst fears are realised with the appearance of an all-too-real, nightmarish creature - The Groke!

Moomintroll employs the services of his new friend, a little ghost, to convince Snork Maiden that he is brave. But when his trick backfires dangerously, Moomintroll is the one who needs saving.