Brother Foulques de Villaret just wants to stay in Acre and perform his sworn duties. Instead, the young Hospitaller Knight of Saint John must undertake a dangerous journey from the Holy Lands to a remote village nestled in the Alps, the "Spine of the World". His mission: buy 500 peasant boys and return them to Acre to be trained as Soldiers of Christ.

Pursued across the Mid-Earth Sea by slavers, Brother Foulques and his Army of Children are about to be thrust into a confrontation with the greatest warriors the East has ever known: the Mamluks. To survive, Brother Foulques must turn to risky alliances… and pray that his choices do not lead them all to destruction.