Marmion

Marmion: A Tale of Flodden Field is a historical romance in verse of 16th-century Britain by Sir Walter Scott, published in 1808. Consisting of six cantos, each with an introductory epistle, and copious antiquarian notes, it concludes with the Battle of Flodden in 1513. 

The poem tells how Lord Marmion, a favourite of Henry VIII of England, lusts for Clara de Clare, a rich woman. He and his mistress, Constance De Beverley, forge a letter implicating Clare's fiancé, Sir Ralph De Wilton, in treason. Constance, a dishonest nun, hopes that her aid will restore her to favour with Marmion. When De Wilton loses the duel he claims in order to defend his honour against Marmion, he is obliged to go into exile. Clare retires to a convent rather than risk Marmion's attentions.

Constance's hopes of a reconciliation with Marmion are dashed when he abandons her; she ends up being walled up alive in the Lindisfarne convent for breaking her vows. She takes her revenge by giving the Abbess, who is one of her three judges, documents that prove De Wilton's innocence. De Wilton, having returned disguised as a pilgrim, follows Marmion to Edinburgh where he meets the Abbess, who gives him the exonerating documents. When Marmion's host, the Earl of Angus (Archibald Douglas) is shown the documents, he arms De Wilton and accepts him as a knight again. De Wilton's plans for revenge are overturned by the Battle of Flodden. Marmion dies on the battlefield, while De Wilton displays heroism, regains his honour, retrieves his lands, and marries Clare. (wikipedia.org)