Prudence is on the pill; so is her sister-in-law, but someone has been swapping aspirin for their pills. Is it the teen-age niece, the maid, the chauffeur, a lover, Prudence's husband, or all of the above?

Gerald and Prudence Hardcastle hardly talk to each other and have separate bedrooms. Gerald consoles himself with his mistress, Elizabeth, while Prudence is having an affair with her doctor, Alan Hewitt. Henry and Grace Hardcastle, Gerald's brother and sister-in-law, are most happily married, but their snug world is upset when Grace becomes pregnant as a result of daughter Geraldine's having substituted aspirin for her mother's birth control pills. Heeding Elizabeth's advice, Gerald decides to do the same with Prudence's pills, hoping she will become pregnant by Alan and get a divorce. His plan is foiled, however, by the family maid, Rose. Thinking Prudence's pills are real, Rose steals them and substitutes what she thinks are vitamins but actually are birth control pills given her by her boyfriend, Ted, the family chauffeur. When Rose rather than Prudence becomes pregnant, Gerald realizes the error and again substitutes aspirin for his wife's pills. Meanwhile, young Geraldine, having run out of pills, becomes pregnant by her boyfriend, Tony Bates, to the consternation of her parents and the delight of Tony's guardian, Lady Roberta Bates. Eventually Prudence does get pregnant by Alan, but her request for a divorce is rejected by Gerald, who has been deserted by Elizabeth. Later, learning that Elizabeth has already given birth to his child, Gerald happily agrees not to contest Prudence's suit, and all the couples celebrate with their babies.