It is one of five plays by Yeats which are loosely based on the stories of Cuchulain[1] the mythological hero of ancient Ulster.
The play is written in verse and opens and closes with the comments and interpretations of the musicians who speak both individually, and as a chorus.
An old man has kept camp there for fifty years, waiting to drink the miraculous waters from the well which occasionally rise up.
While they speak of a hawk which had attacked Cuchulain earlier in the day, and which the old man claims is a supernatural being which carries a curse of discontent and violence, the Guardian of the Well seems to fall into a trance, arises, and begins to dance with hawk-like motions.
Oblivious, he rushes out again to face the warrior women the Guardian of the Well has called out to battle, ignoring the Old Man's pleas to stay with him.