In the Eternal City, Dora and Rex are in a race against time to uncover a murderer, with the future of a political alliance at stake. Rome, 1923. Rex and Dora's holiday comes to an abrupt end when they receive an urgent message from Rome. The Carabinieri have accused the British ambassador of murder. A witness puts the ambassador at the scene and the evidence points to his guilt. But he assures the couple he is innocent...