A special investigator hired to uncover possible sabotage taking place at a deep-sea research station uncovers a crime scene filled with suspects with terrible secrets, strange deep-sea creatures, and an impending flood.

Grissom Callahan, the last in a long line of sheriffs, learned everything he knows from his father and grandfather, but the ways of the old regime don't prove effective when a violent serial killer emerges in their small town. In a single moment of shaking down an informant, Grissom triggers a chain of events that will reshape his life and the world of Texas law enforcement.

The remaining survivors of Dept. H abandon the deep-sea base and prepare for their long-awaited ascent. But life above the waterline remains uncertain for the team, and the pressure to solve Hari's murder continues to strengthen its grip on Mia. Secrets and memories begin to surface, but before Mia can unpack the mystery, she must decide the fate of those still stuck six miles below sea level. As the water rises, Mia's time runs out.

The next entry in the meta-fictional D&D adventure series based on the McElroy family's podcast finds the heroes on a railroad murder mystery involving a genius child detective and an axe-wielding pro wrestler.