The Last Templar, by Raymond Khoury

Published 2005
Since the publication of Dan Brown’s The DaVinci Code, any book mentioning the Knights Templar is bound to intrigue. The story begins with the fall of Acre and the Templar’s last stand in the holy city in 1291. A band of knights escapes from the battle carrying a small chest wrapped in velvet, its contents a well-kept secret, even from all but a few of the Templars themselves. They make their way to the Falcon Temple, a galley ship waiting in the harbor.
Moving forward to the 21st century, four horsemen dressed as Templars ride out of Central Park and into, literally, the Metropolitan Museum of Art where, guns blazing, still astride their horses, they steal several of the items on display at a special showing of Treasures of the Vatican. Witnessing the theft of an unusual object from behind untouched exhibits, Tess Chaykin, is terrified. After the fact, and reunited with her daughter and mother, who had been in the ladies’ room during the commotion, Tess is intrigued. The daughter of a well-known archeologist, and a trained archeologist herself Tess begins to wonder why this particular object was taken.
Sean Reilly is the FBI agent in charge of the investigation. When he questions Tess regarding the incident he realizes that she is holding back something, but doesn’t know what. Tess calls on experts she knows in the field and discovers that the object taken from the exhibit was an encoder, an ingenious device which the Templars used to code messages making them indecipherable to anyone else, even within the Catholic Church. What she and Reilly find out later is that one of the horsemen has discovered one of these messages and needs the device to break the code. Meanwhile the other three horsemen are dropping dead like flies, presumably killed by their leader.
The story continues to flash back to the events immediately after the knight’s escape from Jerusalem in 1291, the path of a small band of knights, the sinking of the Falcon Temple during a storm, the enigmatic reason behind the Knight Templar’s rise to power and subsequent fall. Tess and Reilly, for different reasons, try to stay a step ahead of the lone horseman’s quest to unearth the mysteries of that last ill-fated journey out of the holy land.