When Maria Williams (Maggie McNamara) arrives in Rome to join the staff at the United States Distribution Agency (USDA), the first place her two roommates take her is to the Fountain of Trevi, where it is said that tossing a coin in the water will grant your return to Rome. Maria and Frances (Dorothy McGuire), longtime secretary to the elusive American author John Frederick Shadwell (Clifton Webb), toss in their coins, but Anita Hutchins (Jean Peters) announces that she's returning to the United States in order to get married and doesn't want anything to botch her plans. Not long after, Maria is introduced to Prince Dino di Cessi (Louis Jourdan), known locally as the 'predatory prince'. He invites her to fly to Venice in his plane, but Frances warns her against it. Meanwhile, Anita defies office regulations by spending a weekend with her Italian co-worker Giorgio Bianchi (Rossano Brazzi), who has fallen in love with her. Which of the three will get their wish?