Revenge and retribution have struck down four violent men. Investigations into their past had shown them to have been officers in Salazar's feared secret police. They had committed monstrous crimes against innocent people during that repressive regime. Now was the time of reckoning and they are being systematically killed in England, Portugal, The Netherlands and Germany - but by whom? Met detectives Sam Redwood and Julia Tremaine travel to Lisbon to join the Policia Judicaria in the search for the killers.