A group of monks in medieval Ireland guard a precious religious relic at their rural monastery. Frère Geraldus, a French Cistercian monk, arrives with a charter from Pope Innocent III, commanding the monks to undertake a pilgrimage to transport their monastery's holiest relic to Rome under Geraldus. The monks reluctantly agree as legend tells that the relic's holy power will destroy any not pure-hearted enough to possess it. A handful of monks set out, including multilingual Brother Ciarán and novice Brother Diarmuid, accompanied by a mute laborer. As the group is caught in a rainstorm, the golden reliquary is struck by lightning but shows no damage, further reinforcing the notion of its mystical power.