Ka, the time-travelling cat, has vanished again, leaving Topher a clue in the form of a Roman word on his computer: Ca;;LLevA. At first Topher isn't worried. Surely she's safe among the cat-loving Romans? But when he follows her to Roman Britain, they're both soon swept up in a conflict.

As oppressed Britons fight the Romans, Topher faces a desperate choice - to help his British brother or his Roman friend?