A senior post office official is murdered in his flat. Terzani and Rex's investigations seem to point to the victim's ex-wife, who has never resigned herself to her husband's separation. So many clues seem to lead to her that Gori decides to detain her for further questioning. Terzani and Rex, however, discover that the situation is much more complex and dangerous, as they find themselves on the track of a mysterious dismantled atomic bomb which a gang of Chinese criminals are smuggling through Italy. Having succeeded in intercepting some components of the bomb, the inspector and Rex are still hunting the final piece, containing the plutonium necessary to detonate the device, in Rome's Fiumicino Airport.