When Gifford Hillary is accused of a murder he did not commit, he discovers his soul—or 'Ka'—has the ability to leave his body, allowing him to investigate the crime from an ethereal vantage point. Facing the threat of execution, Hillary must navigate the dangerous intersection of legal peril and occult phenomena. He attempts to clear his name while contending with malevolent forces that seek to exploit his newfound astral projection. The narrative utilizes a third-person perspective to track his movements between the physical world of the courtroom and the unseen realm of spirits and black magic practitioners. His objective remains the identification of the true culprit before his physical body is destroyed.

Readers frequently highlight the unique blend of traditional British legal thriller tropes with Wheatley's signature interest in the occult. Discussion often centers on the technical detail provided regarding the mechanics of the 'Ka' and how it influences the protagonist's ability to gather evidence. Critics note that the pacing reflects the mid-century style of the author, prioritizing atmospheric tension and elaborate plot machinations over rapid-fire action sequences. Many readers appreciate the way the narrative balances the grounded reality of a murder trial with the increasingly bizarre supernatural threats faced by Hillary. The work remains a notable example of how the author integrated esoteric research into popular genre fiction of the era.