Susan's older brother Gary is terminally ill, and Susan is divided between sympathy and resentment at having to look after him. Every day Gary wants her to wheel him through their huge garden, a neglected and somewhat sinister place she has always feared. One day she notices some huge red flowers which have not been there before; their Cambodian gardener Luke says the flowers are opium poppies, which should not grow in Massachusetts. At the pond in the woods, which Susan particularly hates because a child once drowned there, exotic lotus flowers are growing. When the path from the pond impossibly comes out in a different part of the garden, Susan is alarmed but Gary is surprisingly calm.
Susan sees a cloud of small birds flying round the screened porch, but Gary insists there is only one. It is a "quantum bird", being in many places at the same time. Gary explains to Susan the theory of quantum uncertainty and the related concept of multiple universes. He says the garden was designed by their great-uncle, a famous scientist, and he believes it was created to give access to other quantum universes. His illness, itself a random and chaotic event, has triggered the changes in the garden.
Susan's friend Lisa draws attention to the hedge maze, which can be seen from the bathroom window, but which is impossible to find. Suddenly the path to the pond leads to the maze instead, and Gary is eager to go inside. Afraid they will be lost, Susan insists Lisa stays at the entrance while she backs the wheelchair in. Before they reach the first turning they see Lisa dissolve into a cloud of Lisas, and when they go back she says she saw the same happening to them. But the brief excursion into the maze has made Gary much healthier; he is stronger and has an appetite, and the doctor confirms that his blood counts are much improved.
Luke, who knows more than he is telling, is adamant that they should stay away from the maze. Susan becomes aware of other changes, in the house and in their parents, not all positive. The maze has brought them to a different universe. Naturally Gary wants to keep going back in until he is completely well.
The review of this Book prepared by Maureen Evans