Moomintroll faces his toughest challenge yet when he wakes up too early from hibernation. To survive the perils of deepest winter, he must first find his primal side with the help of a strange, ancient ancestor.

When a charismatic winter sports champion arrives in the valley, Moomintroll struggles to win back Snorkmaiden's affections.

As the valley evacuates under the threat of volcanic eruption, Moomintroll helps Snufkin on a perilous quest to return a lost fire spirit to her home.