When Katie finds a box in the attic with two stones in it, she discovers that one of them is a meteorite that fell to earth in the 1940s, narrowly missing a young lad. The other stone is a mystery, and when it begins to grow, no one will believe it. Woven through this story of a spore from outer space that grows into a huge, strangely beautiful, mushroom-like shape are themes having to do with relationships - those of Katie with her school mates, but mainly of Katie with her step- father Chris and stepbrother Jake. She resents their coming into her life and refuses to call Chris dad, her father having moved to America after the divorce. He is portrayed as very much the absent father, while Katie looks for letters and a new address that are slow in coming. The new family is actually a very happy one, and Katie is much more accepting of the situation than she will admit until the end. The changes are subtle and well portrayed, and overall this is a cheeful story with an element of mystery.