It had been raining for days in Moominvalley, but now the clouds had cleared and it was a fine day for an adventure. Moomintroll was excited - he and Snorkmaiden and Little My, Moominpappa and Moominmamma, were all going to sail to Lonely Island to look for treasure! But by the time everyone was ready to leave, the sun had set and night had fallen. Would they ever be able to find any treasure just by the light of the moon?