An aged King Arthur, weary of the burdens of leadership and the inevitability of war, retreats to a final philosophical confrontation with his mentor, Merlyn. As Arthur grapples with the futility of human conflict and the failure of his ideals, he is transported to a magical realm where he must engage in a series of debates and transformations. Merlyn serves as both guide and antagonist, challenging Arthur to reconcile his desire for peace with the inherent aggression of humanity. The narrative unfolds through a blend of whimsical dialogue, surreal encounters, and somber reflection on the nature of power.

This work is widely regarded as the intended conclusion to the Arthurian cycle, offering a stark contrast to the earlier, more lighthearted volumes. Critics often note the shift in tone toward a more somber, didactic exploration of pacifism and the failures of governance. The text is frequently analyzed for its reflection of the author's own disillusionment with the state of the world during the mid-twentieth century. Readers generally approach the book as a necessary, if challenging, coda that provides a definitive philosophical resolution to the character of Arthur.