David Niven and Deborah Kerr star in this British comedy about five couples whose attempts to use a birth-control pill are thwarted by those around them. Banker Gerald Hardcastle (Niven) and his wife Prudence (Kerr) are unhappily married. While Gerald has a mistress, Elizabeth (Irina Demick), Prudence is also having an affair with her doctor Alan Hewitt (Keith Michell). Though Prudence is using a contraceptive pill, Gerald switches her medication in the hopes that she will fall pregnant to Alan and therefore mean he will no longer have to keep his relationship with Elizabeth a secret. Meanwhile, three other couples - the Hardcastle's maid and chauffeur, Gerald's brother and his wife and Gerald's neice and her boyfriend - all want to try the pill for themselves but their secretiveness and scheming leads to more pill switching and a number of possible pregnancies.