Death on the Grand Canal - M. A. Monnin - Bog

Having discovered a knack for investigation, Stefanie joins Thomas Burkhardt in Milan, Italy, on the Black Market trail of a fabulous sapphire and emerald encrusted pendant known as the Borgia Peacock, missing since it was stolen from the Milan World Expo of 1906.

Undercover as a wealthy heiress, Stefanie has no doubt she'll convince the current owner, Contessa Giuliana Bergamo, to sell to her. But when she shows up at the Contessa's crumbling Venetian palazzo to clinch the deal, it isn't only the glittering gemstones that have Stefanie seeing blue. Others are there vying for the Peacock, including Europe's most notorious jewel fence. In the cut-throat competition, one of the would-be buyers is murdered.
Caught up in murder, with their cover identities and their lives on the line, Stefanie and Thomas dig for the truth and the Peacock while trying to avoid discovery themselves. Then she learns Thomas is keeping secrets of his own, secrets that threaten their happiness, and Stefanie wonders if this Borgia Peacock affair is one opportunity she shouldn't have embraced.