"Anyone who intends to present a new story must approach the problem in a new way and speak so persuasively that the tale brings pleasure to people." So does Marie begin this lay with a statement of purpose, after which she states her intention to tell how the name of the lay was composed.
Milun, a knight born in South Wales, was the best knight in all the land, and his inability to be bested in battle or tournaments was known throughout several countries. When a beautiful girl, the daughter of a nobleman, hears tell of Milun, she "conceived a deep love" and sends message to him that she will give herself at his wish. Milun is happy to hear it, and promises his loyalty and love. He asks her messenger to arrange a secret meeting, and sends to her his golden ring as token of his promise. The messenger complies, and the lovers begin to meet in secret, until one day she discovers she is pregnant.
The lady laments to Milun how she will be punished for her sin, perhaps tortured or sold into slavery. Milun promises to do as she asks, and so she asks him to take the child to her married sister in Northumbria to raise. The sister is to be told the entire story but to withhold it from the child until the child is old enough to learn the truth and receive Milun's gold ring. At that point, the child can seek out his or her father.
A trusty old woman servant helps the lady conceal her condition until she gives birth to a son, at which point they prepare the baby for travel. They hang around his neck the ring, a silk purse, and the letter, and give him to Milun, who leaves for Northumbria. He stops to rest seven times a day, and treats the child well on the journey. The girl's sister gladly accepts the baby to raise as her own.
Milun leaves his home to "seek fame as a mercenary." Meanwhile, his beloved is betrothed by her father to a nobleman, which both saddens her from loss of Milun and frightens her since her husband might discover she is no longer a virgin. She laments that she is not free in the world, and must continue to suffer. Her new husband takes her away.
When Milun returns from his travels, sad over his separation from his beloved, he is happy to learn that she now lives near his own home. He composes a plan wherein he sends a letter to her hidden within the feathers of a swan. He entrusts a squire to trick his way into the woman's home to give to her the bird. The squire makes good time to the castle, and there convinces the castle porter that he has caught a lovely swan that he feels obliged to present personally to the lady of the castle. Though the porter initially insists that nobody is able to see the woman, he decides to facilitate a meeting between them. The squire is led to her bedroom, where he gives her the swan. She asks one of her ladies to look after it, but he insists she must receive it herself. It is then that she feels the letter beneath its feathers, and "her blood ran cold."
She is overjoyed to read the letter from Milun, to discover that because of his sadness in being separated, he will do whatever she asks so they can be reunited. He asks her to devise a way for them to meet, and send the particulars through the swan. He tells her to starve the swan for three days and then tie the letter around its neck before releasing it, so that it will surely fly back home for food. She keeps the swan well-fed for a month, after which time she writes the letter, starves the bird, and then sends it to Milun, who is joyful to receive it. He follows the same process to get back in touch with her, always feeding the swan for a while before putting it through the starving again.
The lovers continue this means of communication for 20 years, using the swan as messenger. "No one can be so imprisoned or so tightly guarded that he cannot find a way out from time to time."
Meanwhile, the lady's sister raises the son as a fine youth and becomes a knight. Finally, she tells him of his past, and he is delighted to learn of his father's prowess and fame. He is encouraged by the story to set out and seek even greater fame, to give honor to his family name. He leaves immediately on this mission and heads straight for Brittany, where he quickly gains a reputation as "the best combatant" in all tournaments. He is likewise known for his generosity to poor knights, and becomes known as "The Peerless One."
One knight who is discouraged by the news of the Peerless One is Milun, who does not wish to have his reputation as the best knight eclipsed. Thus, he decides to "quickly cross the sea…to humiliate him and damage his reputation." He plans to defeat the Peerless One and then take advantage of the trip to locate and reunite with his son. He tells his beloved of his plans, and she is happy to hear it.
Milun heads to Brittany, where he passes the winter spending lavishly and making friends. When the season of tournaments comes, he prepares himself and arrives early at his first one, where he is directed towards the Peerless One. Milun performs well that day, but not as well as his adversary. However, he finds himself not only envious but also impressed and proud of the skill displayed by the other.
Finally, the two are paired in a joust. Milun strikes his son hard enough to break the latter's lance-shaft, but does not unhorse him. When the boy strikes Milun back, Milun is unhorsed. The boy sees beneath his father's visor the white hair of age, and is shamed for having shown such aggression. He apologizes for the slight, and asks Milun to remount his horse. Milun is enlivened as he looks up and recognizes the ring on the boy's finger, and he asks the boy to tell his story, saying "You have unhorsed me: I could love you tenderly."
The boy tells his story, and Milun realizes the truth. Thus are they reunited, and spend time together. When Milun tells the boy his own story, the boy promises to kill his mother's husband so that his parents can be united together in marriage. They return together to Milun's land to carry out this plan, but are met immediately upon landing by a messenger who tells them that the lady's husband has died of his own accord. They travel quickly to her, and the family is reunited and "lived night and day in happiness and tenderness."
Many of Marie's lays have messages with complexity belied by the charming or seemingly simple nature of the stories. This is particularly true of "Milun," which praises and celebrates both the nature of the protagonist's love and his desire for fame, while also undercutting both of those elements on closer analysis.
Milun exemplifies the chivalrous value of fame. A knight is expected to compete in tournaments, to test his mettle against his others, and to value such glory above all else. And Milun, as the greatest knight in all the land, clearly embraces this value system. Marie does not explicitly condemn it, but in fact suggests its resonance by having a heroine who falls in love with him merely because of his reputation, sight unseen. Likewise, Milun's agreement to meet her could suggest that what matters most is the flattery of a great admirer (since it is only this that she could have related to him in her initial communication with him).
Lots of the lays explore the way that a secret, private love cannot flourish in a public world, but rarely is the 'world' so exemplified by the protagonist and lover himself. Though his love is selfless – in the vocabulary of the lays in total – and he cares deeply for the woman, he is strangely passive about challenging her husband, something which the son will later immediately agree to do. Their relationship has then to it a romantic and tragic air which perhaps speaks to the chivalrous nature of their relationship (appealing to him), as well as leaving him free to seek fame as mercenary or knight while she stays in a relationship that is not only stifling (the husband is clearly protective) but also dangerous (he might find out she is not a virgin, at which point she could be tortured or sent away as slave).
Marie uses one phrase twice in the lay – "the straightest path." It is this that Milun takes to the woman's sister, and also that the squire takes to first deliver the swan. The suggestion is perhaps that love itself is the "straightest path," the purest emotion, and yet it is corrupted by the forces of the world, in this case the dependence on fame. Notice how the love of fame corrupts the entire family dynamic. The son, when he learns of his heritage, is driven first to honor the family line by seeking fame, rather than attempting to find his parents. This is literally not the straightest path since it involves him going to a different land first. Similarly, when Milun hears about this praised knight, his impulse is to first defeat the knight, and then to seek out his son. The love of their family takes second place to the virtues of chivalry imposed on them by the world, leading them off the straight path. Lastly, this love of fame threatens to corrupt their relationship, since Milun's admiration for the young man's word is tinged with a bitterness and resentment that obviously will need to be overcome to enable the reconciliation.
The swan is an interesting symbol in many ways. The plan to starve it certainly is symbolic of the undernourished love between Milun and his lady, which flourishes briefly in their communications (the same way they feed the swan upon receiving it), but then must go through a period of neglect. However, the swan's continual return home also symbolizes the way that love will find its way to the "straightest path" and right the wrongs. It is a reminder that love is a way out of the crummy world, a possible escape since love in its pure form knows where it should go.
And indeed, this lay has a happy ending that suggests this latter symbolism. Not only is the family reunited, but the husband dies of his own accord. No action is needed, and the secret love is made public in a way that brings happiness to all. Again, the lay is a rather intense criticism of how the world's values will pervert and ruin a pure love, even as Marie shows her storytelling proficiency by making it appear to be a celebration of some same values (Milun is a good guy, after all) and also by framing it so enjoyably. It's a masterful use of irony.
Lastly, this lay shows an intense locality. Marie spends more time than usual naming the locations where the events take place, perhaps to appeal to a particular audience who wished to hear their own homelands mentioned.