Finn was one time out on the green of Almhuin, and he saw what had the appearance of a grey fawn running across the plain. He called and whistled to his hounds then, but neither hound nor man heard him or came to him, but only Bran and Sceolan. He set them after the fawn, and near as they kept to her, he himself kept nearer to them, till at last they reached to Slieve Cuilinn in the province of Ulster.
But they were no sooner at the hill than the fawn vanished from them, and they did not know where was she gone, and Finn went looking for her eastward, and the two hounds went towards the west.
It was not long till Finn came to a lake, and there was sitting on the brink of it a young girl, the most beautiful he had ever seen, having hair of the colour of gold, and a skin as white as lime, and eyes like the stars in time of frost; but she seemed to be some way sorrowful and downhearted. Finn asked her did she see his hounds pass that way. "I did not see them," she said; "and it is little I am thinking of your hounds or your hunting, but of the cause of my own trouble." "What is it ails you, woman of the white hands?" said Finn; "and is there any help I can give you?" he said. "It is what I am fretting after," said she, "a ring of red gold I lost off my finger in the lake. And I put you under bonds, Finn of the Fianna," she said, "to bring it back to me out of the lake."
With that Finn stripped off his clothes and went into the lake at the bidding of the woman, and he went three times round the whole lake and did not leave any part of it without searching, till he brought back the ring. He handed it up to her then out of the water, and no sooner had he done that than she gave a leap into the water and vanished.
And when Finn came up on the bank of the lake, he could not so much as reach to where his clothes were; for on the moment he, the head and the leader of the Fianna of Ireland, was but a grey old man, weak and withered.
Bran and Sceolan came up to him then, but they did not know him, and they went on round the lake, searching after their master.
In Almhuin, now, when he was missed, Caoilte began asking after him. "Where is Finn," he said, "of the gentle rule and of the spears?" But no one knew where was he gone, and there was grief on the Fianna when they could not find him. But it is what Conan said: "I never heard music pleased me better than to hear the son of Cumhal is missing. And that he may be so through the whole year," he said, "and I myself will be king over you all." And downhearted as they were, it is hardly they could keep from laughing when they heard Conan saying that.
Caoilte and the rest of the chief men of the Fianna set out then looking for Finn, and they got word of him; and at last they came to Slieve Cuilinn, and there they saw a withered old man sitting beside the lake, and they thought him to be a fisherman. "Tell us, old man," said Caoilte, "did you see a fawn go by, and two hounds after her, and a tall fair-faced man along with them?" "I did see them," he said, "and it is not long since they left me." "Tell us where are they now?" said Caoilte. But Finn made no answer, for he had not the courage to say to them that he himself was Finn their leader, being as he was an ailing, downhearted old man, without leaping, without running, without walk, grey and sorrowful.
Caoilte took out his sword from the sheath then, and he said: "It is short till you will have knowledge of death unless you will tell us what happened those three."
Then Finn told them the whole story; and when the seven battalions of the Fianna heard him, and knew it was Finn that was in it, they gave three loud sorrowful cries. And to the lake they gave the name of Loch Doghra, the Lake of Sorrow.
But Conan of the sharp tongue began abusing Finn and all the Fianna by turns. "You never gave me right praise for my deeds, Finn, son of Cumhal," he said, "and you were always the enemy of the sons of Morna; but we are living in spite of you," he said, "and I have but the one fault to find with your shape, and that is, that it was not put on the whole of the Fianna the same as on yourself." Caoilte made at him then; "Bald, senseless Conan," he said, "I will break your mouth to the bone." But Conan ran in then among the rest of the Fianna and asked protection from them, and peace was made again.
And as to Finn, they asked him was there any cure to be found for him. "There is," he said; "for I know well the enchantment was put on me by a woman of the Sidhe, Miluchradh, daughter of Cuilinn, through jealousy of her sister Aine. And bring me to the hill that belongs to Cuilinn of Cuailgne," he said, "for he is the only one can give me my shape again."
They came around him then, and raised him up gently on their shields, and brought him on their shoulders to the hill of the Sidhe in Cuailgne, but no one came out to meet them. Then the seven battalions began digging and rooting up the whole hill, and they went on digging through the length of three nights and three days. And at the end of that time Cuilinn of Cuailgne, that some say was Manannan, son of Lir, came out of the hill, holding in his hand a vessel of red gold, and he gave the vessel into Finn's hand. And no sooner did Finn drink what was in the vessel than his own shape and his appearance came back to him. But only his hair, that used to be so fair and so beautiful, like the hair of a woman, never got its own colour again, for the lake that Cuilinn's daughter had made for Finn would have turned all the men of the whole world grey if they had gone into it.
And when Finn had drunk all that was in the vessel it slipped from his hand into the earth, that was loosened with the digging, and he saw it no more. But in the place where it went into the earth, a tree grew up, and any one that would look at the branches of that tree in the morning, fasting, would have knowledge of all that was to happen on that day.
That, now, is the way Finn came by his grey hair, through the jealousy of Miluchradh of the Sidhe, because he had not given his love to her, but to her sister Aine.