All his life, Jack Henley has felt at home in the woods - more at home than when he's actually at home with his parents. He loves watching the badgers play-fighting in the summer evenings, and pretending to be outlaws or cannibals with his two best friends. When Jack discovers that the woods hide an incredible secret - a beautiful, extraordinary, unicorn - he cannot believe his eyes. He and the owner of the woods, the eccentric Mr Finistaire, embark on a journey to save the unicorn from extinction. But as they continue in secrecy, Jack begins to wonder whether Mr Finistaire is quite what he seems. Will the bond between Keras and Jack be enough to withstand the danger that awaits them both?