Dying of curiosity, Lucy (Lucille Ball) and Ethel (Vivian Vance) are determined to get a glimpse of their somewhat secretive new neighbors, Mr. and Mrs. O'Brien (Hayden Rorke, K.T. Stevens). Unbeknownst to the girls, the O'Briens are professional actors, currently rehearsing a play in which they are cast as enemy spies. Hiding in the O'Briens' closet, Lucy (Lucille Ball) is appalled to overhear the couple apparently scheming to blow up the Capitol building. One misunderstanding leads to another, and by episode's end Ethel, Ricky (Desi Arnaz), Fred (William Frawley), and a confused cop (Allen Jenkins) are swept in Lucy's hairbrained scheme to save the country from the "evil" O'Briens.