The Final Reckoning

The Final Reckoning is the third novel in the Deptford Mice Trilogy by Robin Jarvis (first published in 1990).

Plot summary
The ghostly spirit of Jupiter is back, more powerful than ever before. Bent on revenge, he smothers the world in an eternal winter of ice and snow.

Huddled around their fires, the Deptford Mice are worried: the mystical bats have fled the attic, and underground a new rat army is being mustered. With food short and no sign of spring, the mice know that a desperate struggle confronts them. Few will survive.