Yeats’s play is about how a new bride, fascinated by tales of faeries, is eventually taken to the faery world by a faery child whom she welcomes into her home. There are several ways to understand the play.
The play can be read as a testament to the power of myth in the Irish imagination. Mary, the newlywed, is transfixed by a book about faeries she finds in her new home; given the poor nature of the cottage she must share not only with her husband but also with his quick-to-criticize parents, the faery stories offer her a way to escape reality.
The figure of the priest, who is summoned to convince Mary to abandon her interest in faeries, represents the role of religion in Irish life, which is placed in opposition to the faery world. It is only when the priest, at the request of the faery child, removes the crucifix that the child gains its full power and is able to take Mary away. This can be understood either as a failure of faith or as a commentary on the inability of the church to protect Mary—and, in turn, its ineffectiveness in Irish life.
Mary and her husband live in great poverty, and it is clear that the life Mary has ahead of her will offer little hope for change. Her fascination with faeries, then, is an expression of an alternate political or social reality; the faery world is a kind of folkloric response to the social and economic forces that oppress the Irish people.
The chief complaint Bridget has about Mary’s daydreaming about faeries is that she is not doing the work a wife should be doing. Another way of thinking about the faery world is as an escape from traditional gender roles. The faery child, welcomed into the home as a helpless child, is in fact more powerful than all the adults; this power can be thought of as a kind of suppressed feminine power, and Mary’s departure to the faery world as an escape from patriarchy.
Finally, the play can simply be understood as the story of a suicide. Mary’s “escape” into the faery world results in her lifeless body being left behind; faeries notwithstanding, it does seem that she is dead. This death is symbolic of larger issue facing Irish society: namely, the tendency to retreat from reality into fantasy.