Most of the Alliterative Morte Arthure tells of King Arthur's war against Rome, but Arthur and his knights rush back to Britain when they hear that Sir Mordred has usurped the throne. Arthur's fleet crosses the English Channel but waits until high tide to land.
Sir Gawain, not wanting to wait, lands on the shore immediately with a handful of men. Mordred's army is 60,000 strong, and as Gawain is surrounded on the beach, his only regret is that he has led his men to their doom. Gawain and his men fight with surpassing skill, but their strength begins to give out as the battle drags on.
Gawain seeks out Mordred on the battlefield and engages him in combat. Mordred wounds Gawain twice, and finally kills him, leaving his body lying on the ground. The King of Frisia, one of Mordred's allies, asks him who the knight is that he killed. Here I quote (Mordred speaks):
"'Had thou knowen him, Sir King, in kithe there he lenged,
His cunning, his knighthood, his kindly workes,
His doing, his doughtiness, his deedes of armes,
Thou wolde have dole for his dede the dayes of they life.'
Yet that traitour als tite teres let he fall,
Turnes him forth tite and talkes no more,
Went weepand away and weryes the stounde
That ever his werdes were wrought such wandreth to work!"
That is to say,
"Had you known him, Sir King, in his native land,
His wisdom, his knighthood, his kind works,
His actions, his strength, his deeds of arms,
You would grieve for his death all your life."
Yet the traitor (Mordred) at once tears lets fall,
Turns away quickly and talks no more,
Goes weeping away and curses the time
That ever his fate was set such misery to work!
In showing Mordred mourning, the Alliterative Morte Arthure paints a very different picture of the traitor than many other works. It should be noted that in some versions of Arthurian legend, Mordred is Gawain's half-brother. In Alliterative Morte Arthure, Mordred is Gawain's cousin.