The arrival of a church agent on a remote Welsh island to investigate the disappearance of pilgrims triggers a confrontation between rational inquiry and spiritual obsession. Vane, acting as an agent for the church, arrives at a secluded island community tasked with uncovering the fate of missing visitors. He faces opposition from the local Abbot, whose preoccupation with the physical location of the soul creates a barrier to Vane's investigation. The narrative framework utilizes a third-person perspective to contrast the clinical search for evidence against the insular, mystical environment of the island.

Discussion often centers on the stylistic contrast between the grounded investigative plot and the ethereal, poetic nature of the prose. Readers frequently highlight the atmospheric quality of the Welsh island setting, which serves as a character in its own right. Critics often note the philosophical depth regarding the intersection of faith and physical reality. The pacing is described as deliberate, favoring thematic exploration over rapid plot progression. Many readers appreciate the ambiguity present in the resolution, which invites multiple interpretations of the events described.