The Last Templar opens with a hail of fire and flashing sword, as the burning city of Acre falls from the hands of the West in 1291. A young Templar knight, his mentor, and a handful of others escape to the sea carrying a mysterious chest entrusted to them by the Order's dying Grand Master. The ship vanishes without a trace.

In present day Manhattan, four masked horsemen dressed as Templar Knights emerge from Central Park and ride up the Fifth Avenue steps of the Metropolitan Museum of Art during the black-tie opening of a "Treasures of the Vatican" exhibit. Storming through the crowds, the horsemen brutally attack anyone standing between them and their prize. Attending the gala, archaeologist Tess Chaykin watches in silent terror as the leader of the horsemen hones in on one piece in particular, a strange geared device. He utters a few cryptic Latin words as he takes hold of it with reverence before leading the horsemen out and disappearing into the night.

In the aftermath, an FBI investigation is led by anti-terrorist specialist Sean Reilly. Soon, he and Tess are drawn into the dark, hidden history of the crusading knights, plunging them into a deadly game of cat and mouse with ruthless killers as they race across three continents to recover the lost secret of the Templars.