One day all the colors disappear from the valley where the Mumin live. now the trees are gray, the flowers are gray, the multi-colored bridge that Papa Mumin just built is gray, even the river and the sky are gray. Her son, the Mumintroll, together with his friend the little animal Snif, undertake a dangerous mission on a raft downstream to find out if his valley is really threatened by the arrival of a comet. During the trip, they will make friends with a diverse group of creatures. Each one has something that they love most in the world and that they want to save from the cataclysm ... Tove Jansson, known for this series about the inhabitants of the Mumin Valley, created a parallel, magical, friendly and surprising world inhabited by the Mumintroll and his family. Jansson made a bold and novel contribution to Nordic folklore: if until then the troll was a fearsome, clumsy and stupid character, with these children's stories the word troll began to identify with beings who are moving because of their profound goodness and their sense of companionship.