A mysterious artifact, a decoding machine, is smuggled out of the Holy Land into France in A.D. 1291 by Martin of Carmaux, the last Knight Templar, after the siege of their fort at Acre. Many decades later, Martin confesses something shocking about it to a priest on his deathbed, after the Knights have been scattered and killed by King Philippe and the Pope.
A present-day archeologist, Bill Vance (KENNETH WELSH), gets on the trail of the object and steals it from a Vatican treasures exhibit at the Met. Tess Chaykin (MIRA SORVINO), an old acquaintance of his, happens to be at the museum when Vance and his raiding party, caparisoned as knights and riding on horseback, break in and steal the treasures and the decoder.
She then becomes involved with FBI man Sean Daly's (SCOTT FOLEY) pursuit of the thieves, but unbeknownst to them, an assassin hired by the sinister Monsignor De Angelis (VICTOR GARBER), a Vatican emissary who wants to destroy the Templar's secret, is killing the witnesses. At fadeout, Tess, Daly and the assassin are on board a flight to Turkey, following a lead to the hidden treasure.