It’s Jess’s thirteenth birthday. She’s been in bed for nearly a year, the result of a car accident that killed her father.
Surprisingly, she finds a birthday present from her father, an unusual gift for a girl and one which she, her grandfather, and her mother, puzzle over.
In the course of playing with it she discovers that it has some highly-unexpected properties.
But then, purely by accident, she discovers its most amazing feature.
She wonders how she can use this for the benefit of the world, but is foiled by Miss Sturzen, a villainous redhead, who steals the ‘machine’ for her own enrichment and evil ends.
When she captures and imprisons Jess, she has a clear run, but Jess is able to circumvent her difficulties and come up with a particularly appropriate counter strategy, aided by a phlegmatic police sergeant and his retinue of puppies.
Miss Sturzen is arrested and taken away, but escapes and returns to wreak mortal revenge on Jess, using a day and night machine. Unfortunately for her, however, things don’t quite go to plan.
And then we discover the real reason for Jess’s father’s gift.