In the prologue, 1291 Jerusalem is under siege from the Muslims and will soon be in their hands. Martin, a young Templar Knight, his mentor, Aimard, and several other trusted knights are escaping to the sea after being entrusted with a mysterious chest by their Grand Master as he lay dying. The ship vanishes and the fates of the men onboard are unknown.

Fast-forward to present-day New York and the glitzy gala opening of the Treasures of the Vatican exhibit at the Metropolitan Museum of Art. Four horsemen, garbed in medieval armor covered with long, white mantles bearing a red cross, emerge from Central Park and descend upon the museum's entrance. Everyone in the illustrious crowd believes it to part of the opening event, until the horsemen bolt into the museum, smashing, looting and killing as they go. But one of them has only one prize in mind and heads straight to the display case housing an unusual geared device.

Peeking out from her hiding place nearby, archaeologist Tess Chaykin hears the man recite a Latin verse as he reverently lifts the strange contraption of buttons, gears and levers. He then turns and orders the other horsemen to join him as they make their escape.

In the total chaos, confusion and weirdness of the situation, the FBI takes over the investigation. Since 9/11, the threat of terrorist attacks is always at the forefront, so anti-terrorist specialist Sean Reilly is assigned the case. During the interviewing of witnesses, Tess discloses the unusual incident she saw. And her analytical, academic mind starts working overtime trying to figure out just what some of the evidence means to the case.

As the FBI tracks down leads, three of the horsemen are found dead before they can get to them. Someone is murdering everyone involved, but is it the fourth horseman or someone else?

Tess involves herself further in the case as her research points to the ancient Templar Knights. This results in Tess spending more time with Sean. Soon both of them become the target of a deranged madman who will stop at nothing to keep an age-old secret from being exposed. Trying to stay one step ahead of the brutal killer(s), they find themselves caught up in a deadly investigation that takes them to three continents and into horrifying circumstances.

Loaded down with tons of narrative and history on the Templars, as well as extensive tutorials and the ongoing debate between Christian believers and nonbelievers, this novel provides an entertaining fictional account of what the Templars secret treasure really was. The relationship between Tess and Sean has a flat, one-dimensional feel to it. And the only surprising element is the ending. That said, the plot progression did keep my interest and attention as it led to the resolution of the secret.