In the sewers of Deptford there lurks a dark presence which fills the tunnels with fear. The rats worship it in the blackness and name it Jupiter, Lord of All. Into this twilight realm wanders a small and frightened mouse. Far from family and friends he perishes, and in so doing is the unwitting trigger of a chain of events which hurtle the Deptford Mice into a doom-laden world of terror and sorcery.