No sooner have the Ricardos and the Mertzes boarded the Union Pacific Domeliner train for New York than Lucy (Lucille Ball) has accidentally pulled the emergency brake -- and rest assured, it isn't for the last time in this episode. As for the plot, Lucy becomes convinced that a traveling jewelry salesman (Lou Krugman) and a detective (Joseph Crehan) are a pair of crooks, and that a genuine jewel thief (Harry Bartell) is an FBI agent! In the course of events, Fred (William Frawley) and Ethel (Vivian Vance) are splattered with mashed potatoes -- no fewer than three times. ~ Rovi