before merlin passed from the world of men, imprisoned in the great stone by the evil arts of vivien, he had uttered many marvellous prophecies, and one that boded ill to king arthur; for he foretold that, in the days to come, a son of arthur's sister should stir up bitter war against the king, and at last a great battle should be fought in the west, when many a brave knight should find his doom.

now, among the nephews of arthur, was one most dishonourable; his name was mordred. no knightly deed had he ever done, and he hated to hear the good report of others because he himself was a coward and envious. but of all the round table there was none that mordred hated more than sir launcelot du lac, whom all true knights held in most honour; and not the less did mordred hate launcelot that he was the knight whom queen guenevere had in most esteem. so, at last, his jealous rage passing all bounds, he spoke evil of the queen and of launcelot, saying that they were traitors to the king. now sir gawain and sir gareth, mordred's brothers, refused to give ear to these slanders, holding that sir launcelot, in his knightly service of the queen, did honour to king arthur also; but by ill-fortune another brother, sir agravaine, had ill-will to the queen, and professed to believe mordred's evil tales. so the two went to king arthur with their ill stories.

now when arthur had heard them, he was wroth; for never would he lightly believe evil of any, and sir launcelot was the knight whom he loved above all others. sternly then he bade them begone and come no more to him with unproven tales against any, and, least of all, against sir launcelot and their lady, the queen.

the two departed, but in their hearts was hatred against launcelot and the queen, more bitter than ever for the rebuke they had called down upon themselves; and they resolved, from that time forth, diligently to watch if, perchance, they might find aught to turn to evil account against sir launcelot.

not long after, it seemed to them that the occasion had come. for king arthur having ridden forth to hunt far from carlisle, where he then held court, the queen sent for sir launcelot to speak with him in her bower. then agravaine and mordred got together twelve knights, friends of sir gawain, their brother, and persuaded them to come with them for they should do the king a service. so with the twelve knights they watched and waited in a little room until they saw sir launcelot, all unarmed, pass into the queen's chamber; and when the door was closed upon him, they came forth, and sir agravaine and sir mordred thundered on the door, crying so that all the court might hear: "thou traitor, sir launcelot, come forth from the queen's chamber. come forth, for thy treason against the king is known to all!"

then sir launcelot and the queen were amazed and filled with shame that such a clamour should be raised where the queen was. while they waited and listened in dismay, sir mordred and sir agravaine took up the cry again, the twelve knights echoing it: "traitor launcelot, come forth and meet thy doom; for thy last hour is come." then sir launcelot, wroth more for the queen than for himself, exclaimed: "this shameful cry will kill me; better death than such dishonour. lady, as i have ever been your true knight, since the day when my lord, king arthur, knighted me, pray for me if now i meet my death." then he went to the door and cried to those without: "fair lords, cease this outcry. i will open the door, and then ye shall do with me as ye will." with the word, he set open the door, but only by so much that one knight could enter at a time. so a certain sir colgrevance of gore, a knight of great stature, pushed into the room and thrust at sir launcelot with all his might; but sir launcelot, with the arm round which he had wrapped his cloak, turned aside the sword and, with his bare hand, dealt colgrevance such a blow on the helmet that he fell grovelling to the earth. then sir launcelot thrust to and barred the door, and stripping the fallen knight of his armour, armed himself in haste with the aid of the queen and her ladies.

all this while, sir agravaine and sir mordred continued their outcry; so when he was armed, sir launcelot called to them to cease their vile cries and the next day he would meet any or all of them in arms and knightly disprove their vile slander. now there was not one among those knights who dared meet sir launcelot in the open field, so they were resolved to slay him while they had the advantage over him. when sir launcelot understood their evil purpose, he set wide the door and rushed upon them. at the first blow he slew sir agravaine, and soon eleven other knights lay cold on the earth beside him. only mordred escaped, for he fled with all his might; but, even so, he was sore wounded.

then sir launcelot spoke to the queen. "madam," said he, "here may i no longer stay, for many a foe have i made me this night. and when i am gone, i know not what evil may be spoken of you for this night's work. i pray you, then, suffer me to lead you to a place of safety." "ye shall run no more risk for my sake," said the queen; "only go hence in haste before more harm befall you. but as for me, here i abide. i will flee for no traitor's outcry."

so sir launcelot, seeing that at that time there was naught he might do for queen guenevere, withdrew with all his kin to a little distance from carlisle, and awaited what should befall.