Ruby Rogers is about to turn ten. She wants to be a gangster when she grows up. She also wants nothing more than a tree house for her birthday. Problem is, there aren't any trees in her garden, and her family laugh off the idea. Ruby's furious, but then life takes a turn for the better when, through her best friend Yasmin, she meets Holly Helvellyn, a super-cool Gothic girl who's friends with Yasmin's older sister. It turns out Holly rather fancies Ruby's older brother Joe - the brooding artist in the sixth-form who has a strange habit of talking in newspaper headlines. One day Holly asks Ruby to steal something from Joe's bedroom for a joke, setting off a chain of events that culminate in some very unexpected but pleasant surprises ...