This tale must be very old because thatching the house with feathers was a technique actually made in Ireland in olden times. It is interesting note that the drop of sweat that makes the sea, the nut that makes the forest, the hatchet, the duck with the egg and the cock and the hen are very common elements in Irish tales.
One day the king's son met an old man and had a game of cards. The old man put a "geasa" on him not to eat two meals at one table or sleep two nights in one bed until he said: "God save all here".
Looking for help the king's son went to his wise man who said to him: "That man's house is under the sea, if you enter the house he will cut your head with the hatchet he holds in his hand; but once a year his four daughters come as swans to bathe on this island, see what they can do for you". So the king's son did and the four swans came; the youngest decided to help him and said: "My father is sitting at the door and he has the hatchet in his hand to kill you. I will go looking at his head and I will put a sleeping pin in his head till you come in. He won't let you go till he kills you".
So the king's son came into the house and said: "God save all here" and he also said: "My geasa is over now and I can go home". But the old man said: "No, you must build a house for me". The king's son burst in tears because he couldn't build the house, but the young daughter came with his dinner and in the time he ate it the house was built.The old man ordered the king's son to clean the house, to roof the house and to thatch it with feathers; every time he burst in tears and every time the young daughter came with his dinner and, while he ate it, all had been done.
The man's daughter gave reins to the king's son and asked him to take a horse out from the stable; so they ran away on the horse's back. When they were going awhile she said: "My father is coming and his army after him, put your hand in the horse's ear and see if there is anything in it". The king's son did and found a drop of sweat. The girl said to him: "take the drop of sweat and throw it behind us, but let it not fall on me or you". The king's son did so and a large sea appeared between them and the father and the army. The father had to go back home to get a little dish to teem three dishes of water from the sea and so the sea was empty and dry.
Now the king's son and his daughter were near him again, but the girl told her friend to see if there was something in the horse's ear. He took out a little nut and he threw it behind them as he did for the drop of sweat, and a great wood appeared between them and her father. The father had to turn home to take the hatchet to give three blows to one tree and so the forest was cut away.
The young daughter said to the king's son: "Don't forget me and take the duck's egg out from that tree over there, strike with it my father's left arm otherwise he will kill me and you"; but he would not do it and so she struck his father's left arm with the egg and killed him.
The king's son finally went back home and this time the girl said: "You go first, I'll stay outside, but remember not to kiss anyone in the house otherwise you'll forget me". But a young hound kissed him and so he forgot her and got married to a young princess. The man's daughter moved to a nearby village and became a good servant. She had a big boiler out on the road boiling clothes.
One day the young princess came near and wanted to try to turn the clothes into the boiler but she fell into it and died. The king's son was very sad and lonely so he called the village's story-teller in order to drive away the sadness. The story-teller came carrying a small box and she took out a little cock and a hen from it. She also took out a grain of wheat and the cock picked it from the hen. Suddenly the hen started to talk: "Sorrow go from you, cock, you ought not to do that for me. Remember when I put the sleeping pin in my father's head and you say 'God save all here'".
The king's son said: "Throw me another grain of wheat" and the cock ate again from the hen; this time the hen said: "Sorrow go from you, little cock. Remember when I came and built the house my father ordered you, then I cleaned it, I roofed and thatched it for you. Remember also the bridle I gave you". "Now I understand" said the king's son. "I have proved myself very false to you. It was you brought me through the danger, so you'll be my wife".