Trojan Gold by Elizabeth Peters

A mysterious photograph is sent to Vicky through the mail. With no name on the envelope, she is not certain who it came from. The envelope, removed by the overly efficient Gerta, may or may not have been covered in blood. Of course, Schmidt is not going to let this rest. He wants to know exactly who sent the letter and where the lost jewels depicted in the picture went to. Good it be that there is a lost stash of museum items stolen by the Nazis yet to be uncovered?

Vicky doesn't necessarily believe it to be so but she is willing to find out. And maybe that will bring her across the path of her on-again/off-again beau again. 

This book is better in the audio version. The narrator, Barbara Rosenblat, is one of my favorites and bumped it up an entire star. 

Four stars

This book came out in 1987

Follows Silhouette in Scarlet

Followed by Night Train to Memphis

In my Audible library

Opinions are my own