The Charwoman's Shadow by Lord Dunsany

Thus it came about that the Lord of the Tower sent again for Father Joseph, and bade him write him a letter; and the letter was folded and sealed and given to Peter to bear to Ramon Alonzo at the magical house in the wood.

On the day that Father Joseph had left the Tower to go to his own small house the Duke lay in his bed all day very restless. It was the third day of his strange illness. Whenever a step was heard outside his room he watched his door with a fierceness alight in his eyes which only faded from them when he saw Mirandola. He seldom spoke to her, but he could not curse her; he accepted the food that she brought him, and none else ventured near him. And so that day went by and the evening came, and Gulvarez in the room where the boar-spears hung took an old guitar of his host's, that years and years ago Gonsalvo had played; and striking up a tune Gulvarez sang. And the tune was one that so long haunted valleys of Andalusian hills that none knew who first sang it or whence it came. It was a common love-song of the South. The words were vague, and varied in different villages, so that a lover had wide choice how he would sing the song. Gulvarez sang it with a heavy feeling, looking towards Mirandola and singing all the tenderer lines the loudest. When he had finished his hostess thanked him, and Gonsalvo began to tell of old songs that he too had known, but his lady checked him that Mirandola might speak; and they both sat silent, waiting for their daughter to thank Gulvarez.