A Case of Conscience follows Father Ramon Ruiz-Sanchez, a Jesuit priest and biologist sent as part of a scientific expedition to the distant planet Lithia. There, the team discovers a civilization of reptilian aliens who live in a perfectly ordered, rational society—one that appears entirely free of sin, conflict, or superstition. To Ruiz-Sanchez, this presents a profound theological paradox: how can a species exist in moral perfection without any knowledge of God?

As the investigation deepens, Ruiz-Sanchez becomes convinced that Lithia may not be a paradise, but something far more troubling. If these beings truly lack original sin, then their existence challenges the foundations of Christian doctrine. Worse, he begins to suspect that their apparent perfection could be a trap—an illusion masking a deeper, more dangerous truth about the nature of good and evil.

The novel ultimately expands beyond Lithia, exploring the consequences of this discovery back on Earth. Blending science fiction with philosophy and theology, the story examines faith, reason, and the limits of human understanding, raising unsettling questions about whether truth is something humanity is prepared to face.