Yeats tells a story in verse. An old priest was weary and sad because most of his flock had died. He was sent for by a sick man, but fell asleep in his chair before answering the call. The stars multiplied and God talked to mankind.
In the morning, Father Gilligan awoke with a start, realizing that he had not done his duty. He rides to the sick man's house where his wife answers the door and says that the man has died. Father Gilligan is horrified and cries "mavrone!" until the woman thanks him for coming the previous night. He falls to his knees and thanks God for sending an angel down to do his work when he was too tired to do so.
This poem takes a ballad form - a traditional form, usually sung, with regular, short stanzas that tell a story. It has a more overtly religious content than most of Yeats's poems. As a protestant who turned to theosophy and mysticism, Yeats usually stays away from Catholic themes. Yeats also usually stays away from the Irish language, which he uses in this poem when he writes, "mavrone!" which is the Irish, "mo bhron," a cry of grief.
The poem not only speaks to the poverty of rural Ireland, but also to their extreme religiosity. The priest is horrified by the fact that he did not make it to the bedside of the sick man before he died because no one performed the rites of extreme unction, meaning in the Catholic tradition that the man did not die in a state of grace, and therefore cannot go to heaven. The divine intervention which caused this not to be the case is an affirmation of a loving, kind God.
Yeats intends this ballad as an homage to the traditional poetry and legend of his country. He was a collector of similar Irish stories and songs and appreciated their immediate, naive beauty. Certainly this tale draws upon the character as well as the form of the traditional Irish ballad.