Abandoned in a department store as a baby, thirteen-year-old Tom Mullen has been shuffled from one rotten foster home to another his entire life. When he hears rumors that a mass grave has been unearthed on his school grounds, he finds himself inexplicably drawn to it. The grave pulls Tom down into its terrible darkness and beyond, where he discovers that he is no longer in Liverpool in 1974 but in Ireland in 1847, at the height of the potato famine. A family named Monaghan takes him in, and for the first time Tom experiences what it is like to have parents and siblings who care for one another.

But why has Tom been transported through time and space? And why must the grave keep yanking him back to his dreary lonely existence in Liverpool? Most of all, what does it mean that the Monaghan's son, Tully, is practically Tom's double?