The story follows the adventures of Geoffrey and Alys de Villacours, who in 1212 set out on a great crusade of children, bent on making their way to the Holy Land to free Jerusalem. The marching column of children got as far as Marseilles on their own, but were then tricked onto the ships of unscrupulous traders who sold them into slavery. Geoffrey and Alys were separated on that voyage, but both became the slaves of the Governor of Egypt.