This book sees Jansson adopt a darker, more introspective tone compared to the earlier books that is continued in the remainder of the series.
For most of the book Moomintroll is either lonely, miserable, angry or scared - the result of being forced to survive in a world to which he feels he does not belong.
While the rest of the Moomin family are in the deep slumber of their winter hibernation, Moomintroll finds himself awake and unable to get back to sleep.
He discovers a world hitherto unknown to him, where the sun does not rise and the ground is covered with cold, white, wet powder.
Moomintroll is lonely at first but soon meets Too-ticky and his old friend Little My (who takes delight in sledging down the snowy hills on a tea tray).
The friends build a snow horse for the Lady Of The Cold and mourn the passing of an absent-minded squirrel who gazed into the Lady's eyes and froze to death.
As the haunting winter progresses, many characters (notably the Groke, Sorry-oo the small dog, and a boisterous skiing Hemulen) come to Moominvalley in search of warmth, shelter and Moominmamma's stores of jam.