Yeats' The Land of Heart's Desire demonstrates his abiding fascination with Irish folktales and ancient Celtic mythology. He regards the twilight world of fairies, banshees, and ghosts as providing an insight into the mentality of the common Irish people, the rural folk who make up the vast majority of the population of Ireland. Far from seeing such folk beliefs as nothing more than crude superstition, Yeats regards them as a source of enduring wisdom to be handed down from generation to generation.

In telling the tale of Mary, whose obsession with ancient mythology leads to her spirit being led away by a lost child to the Land of Heart's Desire, it's notable that Yeats presents the Catholic Church and its beliefs as incapable of saving Mary's soul. The mysterious child, through open expressions of disgust, has managed to persuade Father Hart to remove a crucifix from the wall. Once this is done, Mary is vulnerable to her mysterious powers. With the crucifix out of the way, the lost child can now work her spell on Mary's soul.

What Yeats appears to be suggesting here is that the old folk beliefs are stronger and more enduring than the Irish people's attachment to formal religion, especially the majority Catholic religion. On this reading, Catholicism may invest the lives of ordinary people with an outward sense of purpose and direction, but it cannot aspire to the same degree of spiritual depth as the ancient legends. When push comes to shove, it's the old beliefs that prevail, more deeply rooted as they are in Ireland's native soil.

This play by Yeats is closely linked to his love of his Irish homeland and the various myths and legends that circulate there concerning faeries and a kind of faeryland where humans were tempted to enter. Interestingly, this was the first of the plays of Yeats to be performed publicly, and it ran in London for about six weeks.

The play concerns itself with the key themes of hopes and dreams and age. Shawn and Maire Bruin are a couple who have recently married. They live in a cottage with Shawn's parents. A faery child enters their life, and is initially welcomed with opened arms by the Bruin household. However, it is clear that there is something suspicious about this child as she stands against Christianity and denounces God. In particular, her function seems to be to focus on how brief life is for humans to try and lure Maire into the faery world where she will know no death and suffering:

Where beauty has no ebb, decay no flood,
But joy is wisdom, Time an endless song.
I kiss you and the world begins to fade.

Although Shawn does his best to try and convince Maire to stay with him, the faery child does kiss her and she dies in Shawn's arms as she is seduced by the thought of life in the faery world and free from human responsibility. Themes of growing old and escape from the burdens of life are therefore key in this play that uses so much of the traditional tales of Irish mythology.