On Christmas Eve, newly appointed justice of the peace Melvin Bush and his wife welcome Stephen Gladwyn and his fiancée Ramona to their home in Gretna Green, Maryland, "the marriage capital of the world." Despite Steve's anxiety about Melvin's inexperience, he and Ramona must marry immediately in order to be hired for a lucrative morning radio show. Melvin performs his first marriage ceremony for Steve and Ramona, who communicate with each other through sarcastic quips. Two years and six months later, Melvin's nephew, the state governor, and his cousin, Attorney General Frank Bush, inform him that he married six couples, including Steve and Ramona, a week before his appointment became official. The problem was uncovered when one of the couples attempted to divorce and found out that their marriage was never actually legal. Stymied over how to approach the remaining five couples, the governor's secretary suggests sending letters informing the couples of the situation and letting them decide how to handle it.
       Ramona and Steve, who have grown to loathe each other, are the first couple to receive the letter, and are overjoyed to learn that they are not really married. Their producer, H. D. Graves, frantically reminds them that their husband-and-wife radio program, Breakfast with the Glad Gladwyns , is the highest-rated morning show, and that if they are not married, they will no longer be making their $5,000 weekly salary. Graves is supported by radio station executive Twitchell, who points out that the Gladwyns signed their contract "Mr. and Mrs. Gladwyn," and must therefore get re-married in order to honor it. Steve and Ramona's quarreling instantly ceases as they begin their commercial-laden show, which is listened to by Melvin and his wife, who are discussing the other four couples.
       The next couple to receive a chance to change their marital status is Annabel and Jeff Norris. Annabel is the statuesque winner of the "Mrs. Mississippi" beauty contest, and although Jeff is proud of his wife, he is dismayed to learn that her promoter, Duffy, intends to keep her so busy that she will not be able to return to her housewifely duties. Jeff is exhausted from caring for their infant son Bitsy, and so, when he receives the governor's letter, he calls the beauty pageant officials to announce that as a single woman, Annabel must be disqualified. Jeff's scheme backfires, however, when Annabel runs for and wins the Miss Mississippi contest.
       Kathleen and Hector Woodruff, the next couple on Melvin's list, have settled into an uneventful life in the suburbs, and are spending their usual quiet evening when Hector reads the governor's letter. Hector indulges in an elaborate fantasy of cavorting with his numerous ex-girl friends in fancy nightclubs, but when he imagines getting the huge bills for the entertainment, he quickly burns the letter before Katie can see it.
       Melvin's fourth ceremony was the wedding of Dallas millionaire Frederick S. Melrose and his exotic, much younger sweetheart Eve. The scheming Eve, who only married Freddie for his money, arranges for him to be photographed in a compromising position in a New Orleans hotel, and uses the photograph to blackmail him for a hefty divorce settlement. Freddie is thunderstruck by the greed of Eve and her lawyer, Stone, and when the governor's letter is delivered to his office, Freddie laughingly sees a solution to his problem. Pretending to cooperate, Freddie lists his numerous assets, then shows the letter to Eve. After Eve faints, Freddie smugly tells Stone that he can pick up his client now.
       The final couple, Willie and Patsy Fisher, bid a tearful farewell at a train station after Willie, a Navy man, is deployed to the Pacific. While the train pulls out, Patsy tells Willie that he is about to become a father, and after Willie reads the governor's letter, he is horrified by the realization that their baby will be illegitimate. Willie jumps off the train and goes AWOL, then telegrams Patsy to meet him in Port City. Patsy reaches their meeting spot, and they rush to city hall to get a license. The clerk gives them the license but informs them that they must be married by the justice of the peace, whose office is across the street. Crossing the street is made difficult by two patroling military police officers, who lose Willie after a brief chase. At the office, the justice of the peace informs the unhappy couple that they must first get a physical report, and Patsy is afraid that it will reveal her pregnancy. All that is needed is a simple blood test, however, but while they wait in the physician's office, Willie is arrested by the M.P.s. As the forlorn Patsy stands at the dock after Willie has been shipped out, a friendly chaplain offers his assistance. Upon hearing the problem, the chaplain arranges for Patsy and Willie, who has been thrown in the brig, to be married over ship-to-shore radio.
       Soon after, Annabel and Jeff are re-married, as are Katie and Hector. Ramona and Steve glumly go to city hall for their ceremony, and when an excited young couple emerges, Steve asks if they can share their rice. Cheered by the gesture, Steve and Ramona realize that they do love each other, and smile as they enter the city clerk's office.