From the burning plains of Syria to the filthy backstreets of Paris and London, Brethren is the story of Will Campbell, coming of age in a time of conspiracy, passion, politics and war.

Will has been brought up from boyhood in the ways of the all-powerful Order of the Knights Templar. With a tragedy in his past that looms over his future, he faces a long, hard apprenticeship to the foul-tempered scholar Everard, before he can have any chance of becoming a Knight. As he struggles to survive in the harsh discipline of the Temple, Will must try to make sense of many things: his own past, the dangerous mystery that surrounds Everard, and his confused feelings for Elwen, the strong-willed young woman whose path seems always to cross his own.

Meanwhile, a new star is rising in the East. A ruthless fighter and brilliant tactician, the former slave Baybars has become one of the greatest generals and rulers of his time. Haunted by his early life, he is driven by an unquenchable desire to free his people from the European invaders of his homeland.