Fleeing the humiliating arrest of her husband-to-be on the eve of their wedding, Celia Kilbride, a gems and jewelry expert, hopes to escape from public attention by lecturing on a brand-new cruise ship, the Queen Charlotte. On board she meets eighty-six-year-old Lady Emily Haywood, "Lady Em," as she is known throughout the world. Immensely wealthy, Lady Em is the owner of a priceless emerald necklace that she intends to leave to the Smithsonian after the cruise. Three days out to sea Lady Em is found dead -- and the necklace is missing. Is it the work of her apparently devoted assistant, Brenda Martin, or her lawyer-executor, Roger Pearson, and his wife, Yvonne, both of whom she had invited to join them on the cruise? Or is it Professor Henry Longworth, an acclaimed Shakespeare scholar who is lecturing on board? Or Alan Davidson, a guest on the ship who plans to spread his wife's ashes at sea? The list of suspects is large and growing. Celia, with the help of her new friends Willy and Alvirah Meehan, who are celebrating their forty-fifth wedding anniversary, sets out to find the killer, not realizing that she has put herself in mortal danger before the ship reaches its final destination.