With a very pregnant Sally at home McMillan, Sgt. Enright and Mildred travel to by train to Los Angeles to attend a police convention. In fact, they're traveling on a train that was chartered for them and about another dozen area policeman by the wealthy Aaron Hildeth. He's also invited Tommy Brown, an author whose recent book revealed supposed police corruption, in the hope that he might develop a more positive impression of the police force. The cops aren't happy to have him on board and one of them even gets into a fistfight with the writer. When Brown is found ...