Retired millionaire Benjamin Dingle comes to Washington and is greeted by a flurry of no vacancy signs, the result of a severe war-time housing shortage in the capital. Upon discovering that he must wait two days to occupy his hotel suite, Dingle scours the classified ads for room rentals. Arriving at a building to find a line of eager applicants waiting to rent the half-apartment described in the paper, the enterprising Dingle pretends to be the lease holder and dismisses the other candidates. When Connie Milligan, the real lease holder, arrives, she expresses reluctance to rent to a male roommate, but Dingle convinces her to grant him a week trial period. After Connie scurries to work the next morning, Dingle meets Sgt. Joe Carter, who has come to inquire about renting the room while he awaits his military assignment. Dingle offers to rent Joe half of his room, and when Connie returns home from work that evening, Dingle tries to conceal Joe's presence from her. Joe's barking in the shower attracts Connie's attention, however, and upon discovering her new tenant in the hallway, she becomes furious and orders both Dingle and Joe to leave. When they demand that she refund their rent, however, Connie allows them to stay because she has spent the money on a new hat. At breakfast the next morning, Joe finds himself attracted to his new landlady. After Connie reveals that she has been engaged for two years to bureaucrat Charles J. Pendergast, Dingle questions the delay and advises her to "damn the torpedoes, full speed ahead." Dingle, who has come to Washington as an advisor on the housing shortage, coincidentally meets the prosaic Pendergast the next day at a luncheon meeting and decides that Joe would be a better match for Connie. One day, Dingle discovers Connie's diary and begins to read aloud the pages that flatter Joe. When Connie discovers Dingle reading her diary, she denounces him and orders both Dingle and Joe to move out the next day. The following day, Connie returns home from work, and Joe gives her a farewell note from Dingle, absolving him of all blame in the diary incident, and then presents her with a traveling bag as an apology. Connie, who has become attracted to Joe, accepts the gift and agrees to let him stay until he leaves for his mission in Africa in two days. When Joe invites Connie to dinner that night, she demurs, saying that she must wait until eight o'clock for Pendergast's call. After the hour passes without a call from Pendergast, Joe and Connie prepare to leave when Connie's neighbor, teenager Morton Rodakiewicz, comes to ask her opinion about joining the Boy Scouts. Morton notices that Joe has taken the phone off the hook, and as soon as he returns the receiver to its cradle, Pendergast calls. As Connie leaves to join Pendergast in the lobby, Joe watches them through binoculars and Morton accuses him of being a spy. After driving Morton away by claiming to be a Japanese agent, Joe goes to meet Dingle for dinner. They arrive at the same restaurant where Pendergast and Connie are dining. When Dingle stops at their table with Joe, Pendergast, who is unaware of Connie's housing situation, invites the two to join them. Determined to unite Joe and Connie, Dingle suggests they dance while he and Pendergast discuss the housing shortage in his suite. On the dance floor, Joe is about to kiss Connie when they are interrupted by a group of Connie's man-hungry women friends. After Pendergast calls Connie to ask Joe to take her home, Connie extracts Joe from the clutches of his admirers, and they walk home together. On the steps outside their apartment building, Joe starts to caress Connie. Flustered, she begins to extoll Pendergast's virtues, and they kiss. Saying goodnight, they retire to their separate bedrooms. Through the wall separating their beds, Connie confides her doubts about marrying Pendergast, and Joe admits that he loves her and proposes. As they murmur endearments to each other, Evans and Pike, two FBI agents, burst into the apartment, having been alerted by Morton that Joe is a Japanese spy. The agents take Joe and Connie to headquarters and also summon Dingle, their ex-roommate, there. Dingle arrives with Pendergast in tow, and when Pendergast learns that Joe shares Connie's address, he is scandalized. After Joe is released when his commanding officer vouches for him, he, Dingle, Connie and Pendergast pile into a cab. Unknown to them, the other passenger in the taxi is a reporter. After accusing Pendergast of being interested only in his career, Connie angrily returns his ring. When the reporter leaves the cab at the headquarters of the Washington Post , Pendergast, terrified of a scandal, follows him. Dingle then advises Joe and Connie to marry quickly and file for an annulment to avoid a scandal. With only twenty-six hours remaining before Joe is to leave for Africa, the couple fly to South Carolina to wed. Upon returning home, the sobbing bride and her groom go to their separate bedrooms. As Joe and Connie nervously pace, they realize that Dingle has had the wall between their rooms removed, and they kiss. Dingle, who has been sleeping in the lobby with a group of roomless men, then steals up to their apartment door and changes the nameplate to read Mr. and Mrs. Sgt. Carter.