Synopsis of Percivale's adventures in Thomas Malory's Morte d'Arthur. Edited by Eugene Vinaver.

Unlike the central role that Percivale plays in De Troyes's and von Eschenbach's narratives, Malory's Percivale is only one of the group of knights that achieve the grail (the other two being Galahd and Bors). Even though he is the knight who has no equal (in prowess of arms and purity) except for Galahad, he plays a supporting role to Galahad in Malory's narrative. Percivale begins his adventures with Lancelot. But soon their paths diverge and he comes across an old recluse who instructs him to ride first to a castle named "Gooth" and then to "Carbonek where the Maymed Kyng ys lyyng" (542). He arrives at the castle where the miamed king and learns about the king's history. King Evelake, was converted to Christianity by Joseph of Arimathea and made a agreement with God that he might never die until he meets a descendant of his that achieve the grail. After four hundred years, he finally sees Percivale in his court and responds with joy in the hope that this is the knight who will achieve the grail.

After departing Carbonek, he comes across twenty knights, who end up trying to slay him. However, he is saved by Galahad, who fights them off. Galahad, however, rushes off after the battle, leaving Percivale alone again. Percivale then meets a wicked knight who slays Percivale's hackney. Without a horse, Percivale is distraught but is then provided with a magnificent horse later that knight by a woman who mysteriously appears. But this horse appears to be possessed or itself a demon and almost charges with Percivale into a dangerous river. But he manages to be preserved as the horse charges into the water by itself.

Perceval then comes across a lion fighting with a serpent. He aids the lion, killing the serpent with his sword and the lion becomes tame, "allwey aboute hym fawnynge as a spaynell" (546). Falling asleep, Percivale has a dream. In the dream, there is an old lady and a young lady. One sits on a serpent, the other on a lion. The young lady, on the lion, speaks to him and warns him that he must fight the strongest knight in the world the next day. The old lady, on the serpent, claims that he has killed her servant without cause and now must serve her in its place. But Percivale refuses.

Waking up, Percivale becomes aware of the sea and sees a ship with an old man onboard. The old man explains Percivale's dream and the actions of the previous day, equating the lion with the teachings of the Church and the serpent with sin. The old man then leaves in the ship. Later on, Percivale spies another ship, this time with a lady onboard. This lady knows who he is and explains that she has been disinherited. Percivale pledges to help her win back her land and is so enchanted by her beauty that he offers his love to her. She, however, rejects it and insists that he pledge to be a true knight. She then undresses, makes a bed and lies down. Percivale, beginning to give in to temptation, undresses and lies down next to her. But by a stroke of luck, he sees the pommel of his sword and is reminded of the Cross, and of his pledge to the grail quest and purity. He cries out to God, thanking him for this sign that has prevented him from committing an even graver sin than he already has. In that moment, the lady exclaims that Percivale has betrayed her and magically drifts off in the ship that brought her. Realizing that he has fallen into some measure of sin, Percivale wounds himself in the thigh with his sword.

The old man and his ship returns and asks how Percivale has fared since they last met. The old man explains that the lady was "the mayster fiend of helle" (551), that she was the old lady of his vision and the strong champion of the warning. Percivale, sobered by his experience, enters the ship and leaves. Percivale thus becomes the first of the grail knights to board the ship that will take them towards the grail. He is later joined by Bors and finally, by Galahad and a lady who happens to be Percivale's sister.

They journey to Logres where they board another ship. Further on in the journey, they come to a waste land and come upon a chapel. There the hermit assures them that they are the knights who will bring the quest for the grail to an end. Coming upon a castle, they are told that it all maidens must submit to the customs of the castle. Initially refusing to agree to give up Percivale's sister to the yet unknown custom, they fight the knights of the castle. But they are then informed that if they knew the custom of the castle, they would agree to it. They learn that the lady of the castle is dying and requires the blood of a virgin who is a King's daughter for her health. Percivale's sister agrees to give her blood and dies as a result.

After a series of adventures that focuses on Galahad meeting his father Lancelot, the three grail knights reunite and head for the castle Carbonek. Entering it, they meet the miamed king, Pelles and his son Elizar. Bors and Perceval fail the test of mending a broken sword but Galahad suceeds. Perceval and Bors are then instructed not to go on to the final stage of the quest, and wait as Galahad achieves the grail and heals the wounded king. The three then depart, with the grail.

On their journey, they are captured and put in prison by the heathen king of Sarras. But the grail feeds them for a year and Galahad is later made ruler over that city when the heathen king dies. The three worship the grail daily until the day that Galahad dies. After Galahad's funeral, Percivale retreats to a hermitage, lives for another year and two months, then dies. Only Bors returns to Camelot and tells the tale to the Arthur's court.