The Last Templer begins with the past. The Templars have just lost Acre and are fleeing with a dangerous secret, then it goes to present day. In the present time it starts with four horsemen, dressed as Templars, riding up to the Metropolitan museum while there is an exhibit on the Vatican. Then it cuts to Tess Chaykin, an archaeologist, while she's with her family in the Met. The horsemen arrive and start killing people. Tess witnesses this and also sees one of the horseman not take anything except for an ancient code breaker while uttering a phrase in Latin. This bothers her so after the FBI come to take care of the mess she investigates. She ends up meeting an FBI agent named Sean Reilly who helps her find answers. Eventually, she goes to find an expert on the Templars, William Vance. However, she soon learns that he is in fact the horseman and the one who orchestrated the museum robbery.
He is obsessed with finding the secret the Templars found and wants to expose the truth. After decoding some letters by the last templar who was at Acre he goes to the Middle East, with Tess and Sean in tow. As they travel they begin to realize that the secret the Templars hid is that Jesus was just a man. The Pope even confirms it in the book. Tess and Sean make it to the place where the map to the truth is buried before Vance, but they are split in their views on what to do when they find it. Sean is a devote Catholic and this truth has rocked his world he wants to keep it under wraps. Tess on the otherhand thinks that this could be her discovery and wants to expose the truth. She ends up joining Vance near the end and they find the truth: papers written by Jesus explaining who he is. Sean catches up to them on the Mediteranian sea where they find it and there is a shoot out between them and the Catholic enforcers sent to stop them. A storm then recks their boat and Sean and Tess are washed ashore. They are banged up but alive. After they heal some Tess takes a walk along the beach and to her surprise finds the papers. She shows Sean but another surprise is in store. Vance is still alive. He finds the papers to but Tess has had a change of heart and no longer wants to expose the truth after realizing how many lives would be ruined. They chase Vance onto these slippery rocks and he falls and dies. The papers are lost to the wind.