Arabella Henderson, a little girl living in Victorian London, often spends time playing with her many imaginary friends, including Sleepytime Sam, a ghost who lulls young children to sleep by playing magical piano music, Jumping Jack, a sprite who jumps around instead of walking, and the Bloom sisters, two flowers the size of humans with women's faces. Ten years later, when Arabella is 16, she returns to her old book where she used to write all those stories about her and her friends, wondering whether they still remember her name and all their wonderful adventures. Unfortunately for her, the truth turns out to be less than pleasant...