One day as Agnar and Geirröth, the young sons of a mortal king, fished from a small boat, a wind drove them away from the shore and across the great sea. In the night their boat wrecked on a strange coast, and a poor peasant couple welcomed them in. The woman cared for ten-year-old Agnar, the heir to the crown, while the man tended eight-year-old Geirröth and taught him wisdom. The boys stayed through the winter with their kind hosts, never guessing that the old man was Allfather Odin himself and the woman was his wife Frigga.
In the spring the old man gave the boys a new boat and sent them homeward. Just before they departed he gave secret instructions to young Geirröth.
A fair wind blew the boys’ boat home to their father’s landing-place. No other person was in sight. Geirröth got out of the boat first, and he pushed the boat and his brother back out to sea, crying 'Go where evil may have thee!' The boat drifted away. Geirröth, going ashore alone, was welcomed, and was also crowned, for his father had died in the winter.
Years afterward Odin gazed from his high seat that overlooked all the worlds, and he laughed, telling Frigga that her fosterling Agnar lived in a cave begetting children on a giantess while Odin’s fosterling Geirröth ruled his realm. Frigga retorted that Geirröth was a miserly king who tortured his guests if he thought there were too many of them making demands on him. Odin denied this, and they made a wager.
Frigga, who knew that Geirröth was not usually a bad host, sent her maidservant Fulla to Geirröth’s hall to warn him of a dangerous enchanter who might be traveling in his direction. The enchanter, she said, could always be recognized by the fact that dogs refused to leap at him.
When a blue-cloaked traveler who called himself Grimnir arrived at Geirröth’s gates and the dogs didn’t threaten him, Geirröth ordered the guards to seize, bind and question him. Grimnir refused to give any information about himself other than his name. Geirröth tried to break Grimnir’s silence by torture, setting him bound between two blazing fires. For eight days Grimnir remained there without food or drink, and the fires blazed so hot that the blue mantle burned on his back.
Now Geirröth had a ten-year-old son whom he had named Agnar after the brother he betrayed. Agnar took pity on the suffering stranger and brought him a horn full of mead to drink.
At this Grimnir broke his silence. First he complained of his pain and ill-treatment, and praised Agnar for his kindness. Then he spoke at length of the beauties of the cities of the gods and of the shaping of the mortal world. At last he raised his face to the gods, called down his divine power, revealed himself as Allfather Odin, rebuked Geirröth’s folly and foretold Geirröth’s instant death.
Hearing this, Geirröth was terrified. He rose with his sword in his hand. Perhaps he only meant to cut his prisoner’s bonds. The sword twisted in his hand and he stumbled, fell on the blade and died.