When a corpse appears in a New Jersey sewer, FBI agents Mulder and Scully uncover a biological anomaly that defies conventional forensic explanation. Tasked with investigating what initially appears to be a standard homicide, the duo must navigate the claustrophobic and toxic environment of the city's subterranean infrastructure. They face opposition from local authorities who prefer to ignore the evidence of a non-human predator, while simultaneously contending with the physical hazards of the sewer system. The narrative follows the established procedural framework of the television series, alternating between Mulder's intuitive leaps and Scully's scientific skepticism as they track a lethal, mutating entity.

This novel functions as a direct adaptation of the iconic television episode, maintaining the established tone and character voices that fans of the series expect. The prose emphasizes the grim, industrial atmosphere of the setting, effectively translating the visual horror of the screen to the page. Readers generally appreciate how the narrative captures the specific chemistry between the two leads while expanding on the procedural details of the investigation. The book serves as a nostalgic artifact for those interested in the expanded universe of the franchise, providing a concise and focused experience that mirrors the original broadcast.