On a fair day Grettir rode west over the Necks to Thorodstead, and came there about noon, and knocked at the door; women came out and welcomed him, but knew him not; he asked for Thorbiorn, but they said he was gone to the meadow to bind hay, and with him his son of sixteen winters, who was called Arnor; for Thorbiorn was a very busy man, and well-nigh never idle.
So when Grettir knew this, he bade them well betide, and went his way on the road toward Reeks, there a marsh stretches down from the hill-side, and on it was much grass to mow, and much hay had Thorbiorn made there, and now it was fully dry, and he was minded to bind it up for home, he and the lad with him, but a woman did the raking.
Now Grettir rode from below up into the field, but the father and son were higher up, and had bound one load, and were now at another; Thorbiorn had set his shield and sword against the load, and the lad had a hand-axe beside him.
Now Thorbiorn saw a man coming, and said to the lad, "Yonder is a man riding toward us, let us leave binding the hay, and know what he will with us."
So did they, and Grettir leapt off his horse; he had a helm on his head, and was girt with the short-sword, and bore a great spear in his hand, a spear without barbs, and the socket inlaid with silver. Now he sat down and knocked out the socket-nail, because he would not that Thorbiorn should cast the spear back.
Then said Thorbiorn, "He is a big man, and no man in field know I, if that is not Grettir Asmundson, and he must needs think he has enough against us; so let us meet him sharply, and let him see no signs of failing in us. We shall deal cunningly; for I will go against him in front, and take thou heed how matters go betwixt us, for I will trust myself against any man if I have one alone to meet; but do thou go behind him, and drive the axe at him with both hands atwixt his shoulders; thou needest not fear that he will do thee hurt, as his back will be turned to thee."
Neither Thorbiorn nor his son had a helm.
Now Grettir got into the mead, and when he came within spear-throw of them, he cast his spear at Thorbiorn, but the head was looser on the shaft than he deemed it would be, and it swerved in its flight, and fell down from the shaft to the earth: then Thorbiorn took his shield, and put it before him, but drew his sword and went against Grettir when he knew him; then Grettir drew his short-sword, and turned about somewhat, so that he saw how the lad stood at his back, wherefore he kept himself free to move here or there, till he saw that the lad was come within reach of him, and therewith he raised the short-sword high aloft, and sent it back against Arnor's head so mightily that the skull was shattered, and that was his bane. Then Thorbiorn ran against Grettir and smote at him, but he thrust forth his buckler with his left hand, and put the blow from him, and smote with the short-sword withal, and cleft the shield of Thorbiorn, and the short-sword smote so hard into his head that it went even unto the brain, and he fell dead to earth beneath that stroke, nor did Grettir give him any other wound.
Then he sought for his spear-head, and found it not; so he went to his horse and rode out to Reeks, and there told of the slayings. Withal the woman who was in the meadow saw the slayings, and ran home full of fear, and said that Thorbiorn was slain, and his son both; this took those of the house utterly unawares, for they knew nought of Grettir's travelling. So were men sent for to the next homestead, and soon came many folk, and brought the bodies to church. Thorod Drapa-Stump took up the blood-suit for these slayings and had folk a-field forthwith.
But Grettir rode home to Biarg, and found his mother, and told her what had happed; and she was glad thereat, and said that now he got to be like unto the Waterdale kin. "Yet will this be the root and stem of thine outlawry, and I know for sooth that thou mayest not abide here long because of the kin of Thorbiorn; but now may they know that thou mayest be angered."
Grettir sang this stave thereupon
"Giant's friend fell dead to earth
On the grass of Wetherfirth,
No fierce fighting would avail,
Oxmain in the Odin's gale.
So, and in no other wise,
Has been paid a fitting price
For that Atli, who of yore,
Lay dead-slain anigh his door."
Goodwife Asdis said that was true; "But I know not what rede thou art minded to take?"
Grettir said that he would seek help of his friends and kin in the west; "But on thee shall no trouble fall for my sake," said he.
So he made ready to go, and mother and son parted in love; but first he went to Meals in Ramfirth, and told Gamli his brother-in-law all, even as it had happed, concerning the slaying of Thorbiorn.
Gamli told him he must needs depart from Ramfirth while Thorbiorn's kin had their folk about; "But our aid in the suit for Atli's slaying we shall yield thee as we may."
So thereafter Grettir rode west over Laxdale-heath, and stayed not till he came to Liarskogar to Thorstein Kuggson, where he dwelt long that autumn.