Eleven-year-old May's life changes dramatically when she leaves the city and moves to Thornton Hall, a big house in the countryside where her grown-up brother Ben has got the job of gardener - despite having been less than truthful about his qualifications!

With her new friend, Alex, May discovers that life at the Hall isn't quite as simple as it seems. What lies behind the locked tower room door that housekeeper Mrs Daniels guards so closely?

As May and Alex begin a journey of discovery, transforming the Hall's overgrown walled garden, Mrs Daniels starts to close in on Ben's little secret. Could May be about to lose Thornton Hall - just as she realises its power to be the making of both her and Alex?