When Grettir had been two winters in Fagraskogafjall and the third winter had set in, he went South into Myrar to the farm called Laekjarbug, where he took six wethers without their owner's permission. Then he went down to Akrar and drove off two oxen for slaughter with several sheep, and went up South to the Hitara. When the bondis heard of his exploits they sent word to Thord at Hitarnes and asked him to take the lead in the slaying of Grettir. He was rather reluctant, but as they had asked him he sent his son Arnor, afterwards called Jarlsbard, to go with them, and told them not to let Grettir escape. Messengers were then sent round to all the farms.

There was a man named Bjarni who dwelt in Jorvi in Flysjuhverfi. He collected men on the other side of the Hitara; the intention was that each band should keep on its own side. Grettir had two men with him, one named Eyjolf, a stout man, the son of a bondi in Fagraskogar, and another. The party came on, about twenty in number, under Thorarin from Akrar and Thorfinn of Laekjarbug. Grettir tried to get out across the river, but was met by Arnor and Bjarni coming from the coast. There was a narrow point jutting out into the river on Grettir's side, and when he saw the men approaching he drove his animals on to it, for he never would let go anything of which he had once got possession. The Myramen prepared to attack in good order and Grettir told his companions to guard his rear. They could not all come on at once. There was a hard struggle between them; Grettir used his short sword with both hands and they found it not easy to get at him. Some of the Myramen fell and some were wounded. The men on the other side of the river were rather slow in coming up because there was no ford near. Before they had been fighting very long they fell back. Thorarin of Akrar was a very old man and not able to join in the fighting. When the battle was over there came up his son Thrand, his brother Ingjald's son Thorgils, Finnbogi the son of Thorgeir, the son of Thorhadd of Hitardal, and Steinolf the son of Thorleif of Hraundal. They set on their men and there was a hard struggle.

Grettir saw that there was no choice left but either to flee or else to do his utmost and not spare himself. He pressed on hard and nothing could hold against him, for his foes were so numerous that there was no chance of escaping except by fighting to the last before he fell. He tried always to engage those who seemed most courageous; first he went for Steinolf of Hraundal and cleft his skull down to his shoulders; then he struck at Thorgils the son of Ingjald and almost cut him in two. Then Thrand tried to spring forward and avenge his kinsmen, and Grettir hewed at his right thigh, cutting out all the muscles so that he could fight no more. Next he gave Finnbogi a severe wound. Then Thorarin ordered them off. "The longer you fight," he said, "the worse you will get from him and the more will he choose out the men from your company."

They obeyed and fell back. Ten had fallen; five were wounded to death or crippled, and nearly all who had been in the battle were hurt. Grettir was terribly fatigued but little wounded. The Myramen drew off, having suffered heavy losses, for many a good man had fallen. Those who were beyond the river came over slowly and did not arrive till the fight was over, and when they saw the plight of their men Arnor would not risk himself any further, for which he was much blamed by his father and by others. Men thought he was not much of a warrior. The place where they fought is now called Grettisoddi.

Grettir and his companions were all wounded; they took their horses and rode back along the foot of the mountain. When they reached Fagraskogar Eyjolf was behind. There was a bondi's daughter there and she asked for their tidings, which Grettir told her fully and spoke a verse:

Then Grettir went to his retreat and spent the winter there.