Every evening Lampie the lighthouse keeper's daughter must light a lantern to warn ships away from the rocks. But one stormy night disaster strikes. The lantern goes out, a ship is wrecked and an adventure begins.

In disgrace, Lampie is sent to work as a maid at the Admiral's Black House, where rumour has it that a monster lurks in the tower. But what she finds there is stranger and more beautiful than any monster. Soon Lampie is drawn into a fairytale adventure in a world of mermaids and pirates, where she must fight with all her might for friendship, freedom and the right to be different.