Amidst steep cliffs and the roaring sea stands a lighthouse, at the top of which lives young Lampie – a brave, curious, and somewhat stubborn girl who has had to take on responsibility too early in life. Her father is a gruff former pirate, now a lighthouse keeper who watches over the sea. When a storm sweeps across the coast and the lighthouse lamp is not lit, Lampie sets off on a quest for matches, which takes her away from the familiar lighthouse and towards the Black House, full of secrets.

The stern admiral's house is looked after by the maid Martha and her son Lennie, who sees the world in his own way. Within the walls of the house lingers the memory of old stories: a monster lurking upstairs. Lampie's courage is put to the test when she encounters a mysterious boy—strange, fascinating, and reclusive. Soon Lampie realizes that things are not as they first appear and that everyone has their own scars and secrets.