The year is 1290. At the twilight of the Crusades, war-weary Knight Templar Jonathan St. Clair is garrisoned in the port city of Acre in the Holy Land. In possession of an ancient scroll with a cryptic inscription, he learns that it holds the key to unlock the secrets of Jerusalem’s Temple Mount.

But time is running out. Acre will soon come under siege, and the one man able to divine the scroll’s meaning, Rabbi Samuel of Baghdad, has been targeted for assassination. St. Clair apprentices himself to Rabbi Samuel and together they travel to Jerusalem. On their pilgrimage, they are hunted by scheming emirs in the service of a bitter enemy of Rabbi Samuel. But they are aided in their quest by others: a brilliant young scholar, Isaac of Acre; a powerful young Scotsman, William Wallace; a learned Muslim mathematician, physician, and cartographer, al-Hasani; and a beautiful independent-minded woman, Zahirah, who avoids serving in an emir’s harem by hiding in a leper colony on the shores of the Sea of Galilee.

Rabbi Samuel, St. Clair and the others will risk everything to fulfill their shared and sacred destiny as guardians of the Temple Mount.