Cosmo's brother Brian died when he was ten years old. His mum hides her grief by working all the hours God sends and Cosmo lives with his grandparents. They've been carefree days as Granddad buys him a horse called John and teaches him all he knows about horses. But the good times have to come to an end and although he doesn't want to admit it, Cosmo knows his Granddad is losing his mind. So on one of the rare occasions when Granddad seems to recognise him, Cosmo is bemused that he gives him a key to Blackbrick Abbey and urges him to go there. Cosmo shrugs it off, but gradually Blackbrick draws him in...Cosmo arrives there, scared and lonely, and is dropped off at the crumbling gates of a huge house. As he goes in, the gates close, and when he turns to look, they're rusty and padlocked as if they haven't been opened in years. Cosmo finds himself face to face with his grandfather as a young man, and questions begin to form in his mind: can Cosmo change the course of his family's future?