W. B. Yeats and the Tribes of Danu is a study of the Irish fairy faith in its ancient and traditional forms, and of Yeats's response to that faith. The first part concerns the ancient beliefs, chiefly as they are expressed in mythology, and describes the origins and characteristics of the Tuatha De Danann. Peter Alderson Smith shows how they are a folk memory of an ancient people who have to some degree acquired divine and ghostly characteristics. Part two describes the fairies of modern folklore, the various types, their charac teristics, and differences from ghosts, in being a separate and supernatural race of people, homogeneous but unpredictable and notorious for their capriciousness. Part three finds in Yeats's work between the writing of The Countess Cathleen (1891-92) and the poems of Responsibilities (1914) a desire to know more about the Otherworld that resulted in a relationship that fluctuated between the poles of frustration and despair on the one hand, and morbid enthusiasm on the other. That the process was ultimately therapeutic is shown by Yeats's move away from the Celtic Twilight to the poems of his maturity.