12-year-old Matthew is trapped in his bedroom by crippling OCD, spending most of his time staring out of his window as the inhabitants of Chestnut Close go about their business. Until the day he is the last person to see his next door neighbour's toddler, Teddy, before he goes missing. Matthew must turn detective and unravel the mystery of Teddy's disappearance - with the help of a brilliant cast of supporting characters.