The Sixth Cache. Things Left Open, #3

In Sfax, a researcher records his grandmother singing the song her mother taught her at the kitchen table. He has heard it eight times. The ninth time, listening back through headphones, he counts the saints in her verse and finds they fall in an order no Orthodox calendar has ever kept. Sami Kouris has spent his career listening to what families do not say. Now the saints' days in a grief-and-numbers song carried from Kalymnos to Tunisia a century ago turn out to be a cipher, and the cipher leads through a Marseille warehouse archive to an unrecorded sixth cache on a Kerkennah island, where his own family is named not as one of the network's protected lines but as its watchers: trusted to see the worst and never to speak.
A disinherited rival wants the secret exposed for profit. The network's last witnesses want it contained. Sami wants neither. He wants it to answer for itself. A standalone novel in the Things Left Open series. For readers of Geraldine Brooks and John le Carre. What does a family owe the truths it was trusted to keep silent?