This mystery finds Lord Peter Wimsey revisiting his first case from thirty years earlier when the descendant of Lord Attenbury begs his help in proving the ownership of a priceless cache of emeralds.

William Gunn wants nothing more than a quiet life. After returning home from the Napoleonic wars, he accepts a position on the Duke of Devonshire's idyllic estate. Destiny, however, intervenes when his young daughter Sarah falls prey to a mysterious sickness, and Gunn must strike out once more into the unknown and search for an unusual cure--the black orchid, a plant found only in the forbidding Amazon rainforest, where the last man who saw it went...

The Thea sisters continue the search for the seven ancient treasures, using the clues found in Aurora Beatrix Lane's travel diary to find a fabulous emerald which once belonged to Cleopatra--a quest that leads them from Moscow, to the Sahara, and finally Bolivia.