As they spoke, suddenly the torches in the hall were extinguished; there was a loud sound like thunder and a sudden cracking of the roof. Then a beam of light, seven times stronger than day, streamed into the room. Across the beam stole the Holy Grail. But it was covered by a luminous cloud, so that its shape could not be seen. Slowly it vanished away.
There was silence in the hall for a long time; the knights were awe-struck and could not speak. At last Sir Perceval rose in his seat and said in a low tone:
"My sister saw the vision of the Holy Grail, but I, because I am more sinful, have seen it covered with a cloud. Yet because I wish to see it, I vow to spend twelve months and a day in search of it. I will pray, and live as holy a life as I can, and perhaps this vision will be mine."
Then good Sir Bors, the cousin of Sir Lancelot, made the same vow, as did also Sir Galahad and Sir Lancelot and Sir Gawain and many others. After the vows had been taken, King Arthur entered. When all had been explained to him, his face grew sorrowful.
"If I had been here," he said, "I should not have allowed you to swear the vow. None of you really saw the Grail; you say it was covered with a cloud."
Then Sir Galahad cried out:
"My king, I saw the Grail, all crimson like a ruby, and I heard a voice which said, 'O Galahad, O Galahad, follow me!'"
"Ah, Galahad," said the king, tenderly, "you are fit for this quest, this search, but the others are not. Sir Lancelot is our strongest warrior, but he is not like Sir Galahad. Most of you, my knights, are men with strength and will to right wrongs; that is the work you are fitted for. You have fought in twelve great battles with the heathen, but only one of you is fit for this holiest of visions. Yet go, and fulfill your vow."
The faces of the knights were downcast. The king continued:
"While you are gone, I shall need your strength here at home, but you will be following a wandering fire. Many of you will never return."