Synopsis of Gawain's adventures in The High Book of the Grail. Translated by Nigel Bryant.

Gawain's quest for the grail in The High Book of the Grail is perhaps the most self-contained and cogently developed of all the grail accounts that involve Gawain. While episodic in nature, this account of his quest for the grail is always keeps the end in clear view. Gawain is never distracted for too long from his quest.

Three maidens come to Arthur's court explaining that the Fisher King, his subjects and his kingdom are gravely suffering because once a knight lodged at the grail castle and neglected to ask about the grail:

Because the knight failed to ask who was served from it, all lands were engulfed by war; whenever a knight met another in a forest or glade they would do battle without any real cause. You can see this yourself: your valour has been waning for a long time. (35)
These maidens leave a shield at Arthur's court, which the chosen knight will use to achieve the grail. But Gawain is not present at this meeting. Instead, he meets the maidens as they are leaving Arthur's court and they encourage him to seek the castle of the Fisher King. The first part of Gawain's journey, until he reaches the land of the Fisher King, comprises a series of disconnected adventures. In this section, he jousts a variety of knights; defends the honor of a lady who is killed by her jealous husband; meets a proud lady who is determined to kill Lancelot, Perceval and himself; and, encounters a wonderful child who has tamed a lion. These seemingly disconnected incidents will later be explained as a spiritual allegory that recounts the fall of man and his redemption through Jesus Christ.

Gawain then comes to the entrance to the land of Fisher King:

He turned that way and rode towards it, and soon he could see the great wall that surrounded it and the strong castle gate. And lying in the middle of the gateway he saw a lion, chained to the wall, and on either side of the gate stood two ghastly figures of copper, which by an ingenious device could fling forth crossbow-bolts with great strength and fury. (61)
Here he learns that in order to enter the land of the Fisher King, he must have in his possession the sword that was used to behead John the Baptist. On learning this, he sets out to search for the sword, a quest that forms a second series of adventures.

As he journeys on his quest for the sword, he learns that it is in the possession of King Gurgaran. Along the way, as he makes his quest known, a townsman and then the King of the Watch request that Gawain show them the sword in exchange for a horse and for directions. Gawain promises that he will show them the sword on his return from King Gurgaran.

When he arrives at King Gurgaran's castle, he is tasked with rescuing the king's only son, who has been abducted by a monstrous giant. Only then will the king give Gawain the sword:

The king bade that the sword be brought, and he showed Gawain the scabbard first, all inlaid with precious stones; and the straps were made of silk with golden studs; and the hilt was of gold likewise; and the pommel was a hold, sacred stone which Evalus. a noble emperor of Rome, had mounted there. Then the king drew the sword from its sheath, and out it came, bleeding for it was then noon, and he bade that it be held before Gawain until that hour had passed. Thereupon the sword became as bright and green as emerald. Sir Gawain gazed at it in wonder, coveting it more than ever. (69)
Gawain slays the giant but in the struggle, the boy is strangled by the giant. Gawain returns with the dead boy and the head of the giant. Though King Gurgaran is filled with grief, he honors his promise and gives Gawain the sword.

Tracing back his steps, Gawain fulfills his promises to the King of the Watch and the townsman to show them the sword. They both try to steal the sword but Gawain manages to retrieve the weapon. Just before he returns to the land of the Fisher King, he stops by the Castle of Enquiry. Here, the significance of his adventures are explained to him. For example, when he asks about the child who managed to tame a lion, he receives the following reply:

"You have spoken well," replied the priest, "in reminding me of that. The child signifies the Saviour of the world, who was born into the Old Law and was circumcised, and the lion he was riding signifies the world and the people in it, and the animals and birds, for only He with His divine power could govern them and bring justice to them." (74)
As the earlier episodes are recounted and their spiritual significance unfolded, it becomes clear that they were meant to purify Gawain to prepare him to enter the Castle of the Fisher King and achieve the Grail.

Armed with the sword, Gawain passes easily into the land of the Fisher King and into his castle. He is greeted warmly by the Fisher King, to whom he presents the sword that beheaded John the Baptist, who declares that he must be a good knight, having managed to enter the castle. The Fisher King reminds Gawain to speak up that night, when the grail appears, in order that the king's suffering be put to an end. During the feast that night, Gawain sees the lance with the bleeding tip and the Holy Grail. However, he is so entranced by the sights that he forgets to speak, even as the knights look on in dismay. Having lost his opportunity to heal the Fisher King and the kingdom, Gawain can only ride away from the castle in shame.