The Time of Green Magic

Abi and her two step-brothers, Max and Louis, find that strange things happen when they are alone in their eerie, ivy-covered new house. Abi, reading alone, finds herself tumbling deep into books, while Louis summons a startling guest through his bedroom window. Even Max has started to notice shapes in the shadows. Their busy parents see none of it — but Louis' secret visitor is growing too alarming to keep hidden, and he finds he cannot manage without Max and Abi's help.
Can they find out where the mysterious creature has come from — and how to get it back there ?