Jimmy Costello, hard-man and bad catholic is back and he's studying to be a priest. The same corrupt London CID Sergeant who was last seen in Bad Catholics at the epicentre of a murder investigation and a gangland turf war is now at Duns College in Rome. He may have thought that he could put his old life behind him but Jimmy's past refuses to stay buried.

When a visiting Archbishop dies in mysterious circumstances, Jimmy is hand-picked by the Church authorities to look into the case. With local copper Inspector Ricci, Jimmy follows the investigation from the streets of the Holy City via Glasgow and an old friend, back to Rome where they stumble on a devastating plot. But who is responsible? Jimmy's problem is that he's too good a detective.

Secrets have a way of finding him out but maybe this is a secret too far.