July 1099: sweltering in the merciless heat, Godefroi de Bouillon's desperate army finally breaches the walls of Jerusalem. Concealed within their ranks are members of a secret fraternity. The Salt Lines seek a mystical artefact called the Keystone, and they're willing to sacrifice everything Godefroi values to possess it: the lives of his closest confidants, the only woman he has ever loved, even his very soul.

October 1307: when Bertrand de Châtillon-sur-Seine joined the Brotherhood of the Temple of Solomon, no one anticipated the brutal suppression of the Order that was to follow. Forced to flee for his life, Bertrand unwittingly becomes the only person who can lay the Keystone to rest. But can he resist its temptations whilst eluding agents sent by the man who stands behind the French throne?

With the veil of secrecy in tatters, truth has become the most dangerous possession of all.