"Dr. Luke," said Rita Wainright, "I'm terribly, horribly in love with Barry Sullivan." "What about your husband?" "He doesn't know!" But was Alec Wainright ignorant of the fact that his beautiful young wife was having an affair? And what possible solution was there for Rita and Barry with Alec standing in their way, so old, so ill, and so devoted? Then one black night the unexpected happens. and that's where Sir Henry Merrivale comes in. The great H.M. has a nasty time with this ironclad puzzle.