Three days of rain turn a quiet Missouri spring into a crime scene when human remains surface from the limestone depths.

Forensic investigator Dr. Cassian Holt and K9 handler Jonah are called to Ozark Springs State Park, where the evidence points beyond one body and into a hidden underground disposal operation. Chemical traces, deep-cave water patterns, missing workers, and ignored disappearances begin to form a chilling map of exploitation, corruption, and murder.

As the Critical Trace team follows the case into flooded passages and industrial cover-ups, Cassian and Jonah must balance professional precision with a relationship already tested by fire, danger, and trust. Their bond is no longer a secret between cases. It is the force that keeps them moving when the investigation descends into darkness.

Limestone Nightfall is a thriller-forward MM romantic suspense novel for readers who want forensic investigation, dangerous settings, protective partnership, found-family teamwork, and a mystery that reaches from rural cave systems to corporate power.