The Sea Fairy

One evening, while walking home from the fields, a young man notices some sea fairies dancing on the sea shore. They do this whenever the moon is full, discarding their mermaid tails and using this freedom to dance. The man notices that one of the tails is hidden by his shadow and when the sea fairies see the man watching them they slip on their mermaid tails and plunge into the sea. One of the fairies is unable to do this as she cannot find her mermaid tail. Quickly the man hides the missing tail behind a rock and goes to the stranded fairy. He notices how beautiful she is and asks her to marry him. Realizing that she has no option the fairy agrees. The couple are married by the priest and go to live in the man's cottage.  The man and the fairy love each other and are very happy. As the years pass four beautiful children were born to them but the man notices that occasionally the fairy is often seen at the sea's edge calling to her own people. One day while playing in the fields the children find the missing mermaid tail.
What will the sea fairy do when she sees the missing tail?  An Irish myth.