Aotrou and Itrou are Breton words for "lord" and "lady". The poem is modelled on the genre of the "Breton lay" popular in Middle English literature of the 12th century, and it explores the conflict of heroic or chivalric values and Christianity, and their relation to the institution of marriage.
In the poem, Aotrou and Itroun are a couple of Breton nobility. They are childless, and Aotrou seeks the help of a witch. When Itroun is with child, the witch reappears, revealing herself as the Corrigan, and asks for Aotrou's love as payment. Aotrou sacrifices his knightly honour to Christian values, and breaks his word.
Cursed by the Corrigan to die in three days, Aotrou takes the consequences and places his trust in Providence:
Aotrou passes away after three days, his wife dies of broken heart and they are buried together, and they do not live to see their offspring grow up.