Chrétien de Troyes's masterpiece Lancelot, The Knight of the Cart is a riveting tale of knightly valor and courtly love. This romance marks the first known appearance of Lancelot as a major player in the Arthurian canon, and it also provides the first account of his affair with Guinevere.
The first half of the narrative follows Lancelot (then unnamed) as he rescues Guinevere, who has been taken hostage by the evil Méléagant. Méléagant visits Arthur's court, boasting that he has ensnared many from Arthur's land (Logres). He ultimately convinces Arthur through trickery to give him Guinevere, and sets out to bring her to his homeland of Gorre as another prisoner.
When Lancelot ends up without a horse, he encounters a dwarf with a cart, who claims to have information about the queen's whereabouts. However, he will not share his information unless Lancelot ride in his pillory cart, which is usually reserved for criminals, and hence brings shame to any who ride in it. Lancelot nevertheless rides in the cart, which brings him much shame and causes confusion amongst many he encounters.
On the way to Guinevere, Lancelot is aided by a number of beautiful women and kindly girls. He encounters hostile and arrogant knights, and must constantly defend his character. Initially, he travels with Sir Gawain, but they eventually part to take different routes to Gorre. Lancelot chooses the faster, more dangerous rouge of the Sword Bridge, which is literally a large sword blade.
He arrives in Gorre, to discover that Guinevere is angry with him, for reasons she does not initially disclose. There, he also discovers that the ruler is the kindly and reasonable King Bademagu, who stands in stark contrast to his mischievous son Méléagant. Rebuked by Guinevere, Lancelot leaves to find Sir Gawain, who attempted to cross a different bridge, and has not been seen. While Lancelot is gone, Guinevere hears false rumors of his death, and decides to show him warmth. Lancelot returns to Bademagu's court, and Guinevere confesses that her coldness resulted from the hesitation he showed before leaping into the cart.
Reunited, they share a passionate night together, but Lancelot bleeds on her sheets, and Méléagant accuses her of adultery. To defend her honor, Lancelot fights Méléagant. King Bademagu intercedes to end the battle, and Lancelot promises to fight Méléagant within a year's time at King Arthur's court. By this time, the people of Logres are free to leave Gorre.
If the first half of the narrative centers around Guinevere’s imprisonment, the second half is driven by Lancelot’s incarceration.
Lancelot and his party set out again to find Gawain, but Lancelot is tricked by a devious dwarf, a henchman of Méléagant, who takes him captive. A fake letter from Lancelot is sent to Guinevere, insisting she return to Arthur’s court, where she will find him. Meanwhile, Lancelot's party finds Gawain, who is also fooled by the letter.
Returning home, they realize that Lancelot must have been captured. Méléagant soon arrives to demand his battle with Lancelot; Gawain promises to fight in Lancelot's stead, and they plan to fight within a year's time.
In the meantime, a tournament is organized, over which Guinevere is to preside. Lancelot hears about the tournament, and convinces his jailer's wife to grant him temporary freedom so he might compete. When he arrives at the tournament, wearing unknown armor, Guinevere nevertheless recognizes him because of his valor in battle. To test his identity, she sends a message that he should fight badly, and he complies. She then reverses the message and triumphs, but then promptly disappears to return to his imprisonment, as he promised the jailer's wife he would do.
Upon Lancelot's return, Méléagant imprisons him in an impossibly tall, impenetrable tower. When Méléagant's sister, for whom Lancelot had previous done a kindness, learns of the great knight's disappearance, she rescues him and helps him recover from his weakness.
Lancelot then returns to Logres, at the moment when Gawain and Méléagant are to battle. Lancelot steps in to vanquish the evil Méléagant, and the romance comes to a triumphant close.