Dr. Watson has been the right-hand man of master sleuth Sherlock Holmes through many a mystery, always there to fit a missing piece to the puzzle. But now Watson has gone missing. Lacking even the slightest clue, Sherlock enlists the assistance of Enola Holmes, his intrepid kid sister. Enola readily takes the case, for Watson is dear to her as well. She quickly learns, however, that danger will be afoot down every lead she might explore. Going first to Watson's home, she investigates just in time to witness the delivery of a bizarre bouquet blooming with convolvulus, hawthorn, and white poppies—flowers that symbolize death!