Airline pilot Adam Tyler's plans to spend a romantic weekend in his New York apartment with Mona Harris are interrupted by the unexpected arrival of his sister Eileen, who has just quarreled with her fiancé, Russ Wilson, because she refuses to sleep with him before marriage.  After assuring Eileen that she has done the proper thing and advising her to remain a virgin, Adam persuades Mona to accompany him on his next flight.  His assignment is changed at the last minute, however, and he is unable to reach Mona, who is stranded in a strange city.

Meanwhile, Eileen finds evidence of her brother's double standard, and when she meets Philadelphia newspaperman Mike Mitchell on a Fifth Avenue bus, she becomes determined to seduce him.  Mike respects her virtue and is reluctant to comply, even though both of them soon realize they are falling in love.  After getting caught in a downpour, they take refuge in Adam's apartment and are surprised by the arrival of a forgiving Russ, who mistakes Mike for Eileen's brother.

Upon his return Adam is introduced as his own co-pilot but goes along with the masquerade, even though he suspects the truth.  The situation is resolved later that evening: Mike and Eileen admit their love; Russ, believing that Eileen has been unfaithful to him, admits defeat; and Adam decides it will be easier to marry Mona than to arrange illicit meetings with her.