Before he had a family, Moominpappa led a life of adventure and intrigue. But he's never told his story until now. He has a bad cold, and it's the perfect time to remember his youthful endeavors and to ponder the experiences which have made him the remarkable Moomin he is.

When a flood sweeps through the valley, the Moomins must find a new house. And with typical Moomin good luck, one just happens to be floating by. It looks normal enough, but there are curtains where one wall should be, strange rows of lights, and other odd amenities. Then Moomintroll and the Snork Maiden disappear, and the family realize that the house may hold the answers to more than they ever dreamed.

Everyone knows the Moomins sleep through the winter. But this year, Moomintroll has woken up early. So while the rest of the family slumber, he decides to visit his favorite summer haunts. But all he finds is this strange white stuff. Even the sun is gone Moomintroll is angry: whoever Winter is, she has some nerve. Determined to discover the truth about this most mysterious of all seasons, Moomintroll goes where no Moomin has gone before.