Suzy Button is grieving. Grieving for her dead mother, but also for the friends she's left behind, the father who no longer laughs and the life that she once had. In desperation she finds herself in the garden in the middle of the night, under the light of a supermoon, wishing everything would change. And suddenly, it does.

Into school walks Rhiannon, a fearless new girl who makes Suzy her instant best friend. And Rhiannon seems to make things . . . happen. If Suzy wants something, somehow Rhiannon can make it so: friends, beach parties, midnight photoshoots under a moonlit sky . . . Suzy's life is finally moving forward again.

But where did Rhiannon come from? She doesn't seem to live in Sallycove. Why can't Suzy go to her house? And why does she never have any stuff? Suzy might be her best friend, but does she really know who Rhiannon is?