She hadn't shared her husband's bed in eight years, but well-named Prudence Hardcastle was taking contraceptive pills. Gerald Hardcastle was an unimaginative sort of tycoon, but one day he heard a story that carried him away. Seems his niece (Ha, Ha) had been filching her mother's contraceptive pills and replacing them with aspirin. Now (Ha, Ha) his good natured, middle aged sister-in-law was quite preggers. Shortly after hearing this, Gerald stumbled on his wife's cache of preventives. With barely a pause between thinking, ""Aha!,"" and substituting the first aspirin, this delightfully bright drawing room comedy of a novel out of England involves the chauffeur and the maid and Gerald's mistress. It all hangs and swings by the most delicately poised Damocles of a pill -- and in good taste. It's an elegant romp based on a case that was supposed to have actually happened.