The last secret of the temple / Paul Sussman.

Enhanced descriptions from Syndetics:

Jerusalem, 70 AD. As the legions of Rome besiege the Holy Temple, a boy is given a secret that he must guard with his life...Southern Germany, December 1944 . Six emaciated prisoners drag a mysterious crate deep into a disused mine. They too give their lives to keep the secret safe: murdered by their Nazi guards... Egypt, Valley of the Kings, the present day. A body is found amongst some ruins. It appears to be an open-and-shut case for Inspector Yusuf Khalifa of the Luxor police. But what begins as a routine investigation rapidly turns out to be the most trying case of his career. Forced into an uneasy alliance with Arieh Ben-Roi, a hard-drinking Jerusalem detective, and Layla al-Madani, a daring Palestinian journalist, Khalifa enters a murky, murderous world of greed, duplicity, intrigue and revenge as he goes in search of an extraordinary long-lost artifact that could, in the wrong hands, turn the Middle East into a blood bath. Traveling from ancient Jerusalem to contemporary Egypt, and involving Cathar heretics, coded medieval manuscripts, and hidden Nazi treasures, The Last Secret of the Temple is an absorbing thriller set against the tumultuous politics of the present-day Middle East.