When stricken with a severe cold, Moominpappa decides to set down an account of his eventful youth, which he shares chapter by chapter with Moomintroll, Sniff, and Snufkin.
The Finn Family Moomintroll awakens from a long winter's sleep and embarks on a whole new set of adventures, including the discovery of a magic top hat that can turn anything or anyone into something else.
Moomintroll encounters a mouth organist, a moth collector, and a lovely maiden, and discovers the danger of a threatening comet when he takes a journey to seek advice from the Professor.