So, that evening, when all were gathered about the Round Table, each knight in his own siege, suddenly there was heard a crash of thunder, so mighty that the hall trembled, and there flashed into the hall a sun-beam, brighter far than any that had ever before been seen; and then, draped all in white samite, there glided through the air what none might see, yet what all knew to be the Holy Grail. And all the air was filled with sweet odours, and on every one was shed a light in which he looked fairer and nobler than ever before. So they sat in an amazed silence, till presently King Arthur rose and gave thanks to God for the grace given to him and to his court. Then up sprang Sir Gawain and made his avow to follow for a year and a day the Quest of the Holy Grail, if perchance he might be granted the vision of it. Immediately other of the knights followed his example, binding themselves to the Quest of the Holy Grail until, in all, one hundred and fifty had vowed themselves to the adventure.
Then was King Arthur grieved, for he foresaw the ruin of his noble Order. And turning to Sir Gawain, he said: "Nephew ye have done ill, for through you I am bereft of the noblest company of knights that ever brought honour to any realm in Christendom. Well I know that never again shall all of you gather in this hall, and it grieves me to lose men I have loved as my life and through whom I have won peace and righteousness for all my realm." So the King mourned and his knights with him, but their oaths they could not recall.
Great woe was there in Camelot next day when, after worship in the Cathedral, the knights who had vowed themselves to the Quest of the Holy Grail got to horse and rode away. A goodly company it was that passed through the streets, the townfolk weeping to see them go; Sir Launcelot du Lac and his kin, Sir Galahad of whom all expected great deeds, Sir Bors and Sir Percivale, and many another scarcely less famed than they. So they rode together that day to the Castle of Vagon, where they were entertained right hospitably, and the next day they separated, each to ride his own way and see what adventures should befall him.
So it came to pass that, after four days' ride, Sir Galahad reached an abbey. Now Sir Galahad was still clothed in red armour as when he came to the King's court, and by his side hung the wondrous sword; but he was without a shield. They of the abbey received him right heartily, as also did the brave King Bagdemagus, Knight of the Round Table, who was resting there. When they had greeted each other, Sir Galahad asked King Bagdemagus what adventure had brought him there. "Sir," said Bagdemagus, "I was told that in this abbey was preserved a wondrous shield which none but the best knight in the world might bear without grievous harm to himself. And though I know well that there are better knights than I, to-morrow I purpose to make the attempt. But, I pray you, bide at this monastery awhile until you hear from me; and if I fail, do ye take the adventure upon you." "So be it," said Sir Galahad.