Famous London-based theater actress Anna Kalman Ingrid Bergman is bored with her latest romantic infatuation and has returned home early from a trip to Mallorca. Her sister Margaret Munson Phyllis Calvert and brother-in-law Alfred Munson Cecil Parker arrive at Anna's apartment with Philip Adams, a handsome American economist who Alfred hopes will accept a NATO post in Paris. Phillip Adams Cary Grant is charming and quick-witted, and the group convinces Anna to attend the dinner lecture that he is giving on economics, even though she’d rather skip another lengthy talk. Philip’s humor about mundane speeches does little to hide the fact that he’s being courted for a high-stakes assignment, and Anna finds herself drawn to his easygoing warmth.
After a pleasant evening, Anna invites Philip to the ballet, and he confesses something that could complicate any growing romance: he is married, and while separated, he cannot divorce. Anna wrestles with the truth but, moved by attraction and a desire to see him again, she invites him anyway. He accepts with a smile, and the two begin to spend time together, developing a connection that grows into a real romance. The arrangement evolves as Philip’s NATO duties require travel, and he accepts a temporary transfer to Paris that would let him visit London frequently, even as a longer stay in New York is also in the plan.
As their relationship deepens, Alfred privately reveals to Philip that he knows Philip is a bachelor and questions why Philip had told Margaret he was married. Philip insists that he has no intention of marriage, arguing that the so‑called honorable approach—telling women he’s married to avoid commitment—backfires by feeding their fantasies of romance. Alfred remains unsure about Philip’s approach, but he agrees to keep the secret for the sake of friendship. Philip tells Alfred that he truly loves Anna and plans to delay his departure after the NATO team sails so he can surprise Anna at midnight on her birthday and spend a few more days with her before joining the group in New York.
When Anna learns she might have to wait five months without Philip, she shares her fear with Alfred and Margaret. Alfred discloses Philip’s plan to surprise Anna, and Margaret bluntly reveals she has learned from a Scotland Yard security report that Philip is unmarried, which inflames Anna. In a moment of impulse, she crafts an elaborate plan to avenge the deception by pretending to have an affair with David, an old flame, so Philip will be confronted by a supposed indiscretion on her birthday night.
Things spiral when David is hospitalized with a sports injury, so Anna pivots to a backup ruse. She enlists her elderly butler, Carl David Kossoff, to stand in as David, stepping out of her bedroom in a silk robe as the clock nears midnight, casting a shadowy figure into Philip’s line of sight as he arrives to surprise her. They rehearse the moment to ensure the timing is perfect, while Philip, meanwhile, has begun questioning his bachelorhood and the road he’s chosen.
When the clock strikes midnight on Anna’s birthday, Philip arrives with a bracelet of diamonds and, in a moment of confession, proposes marriage. Just then, Carl slips into the room, creating a tense misunderstanding. Before Anna can explain, Philip’s anger at her supposed infidelity flares, and he leaves. But he soon returns, and Anna reassures him, clearing up the confusion. The two acknowledge their deceptions and recognize that they might be happier if they simply forgave themselves and embraced what their romance had become. Yet Philip remains determined to marry, and Anna, moved by joy and relief, welcomes the idea. The film ends with them embracing, the couple choosing a future together and ready to face whatever comes next.
