Limestone Nightfall

By Miles Ashbourne

Two men who built their partnership on science and trust must now gamble both on each other—because in the dark, the only thing more dangerous than a killer is the truth they've been hiding.

Dr. Cassian Holt operates best in controlled environments—sterile surfaces, precise measurements, evidence that never lies. When a karst spring in rural Missouri surrenders a chemically etched skull after three days of flooding, his forensic instincts fire on all cylinders. But beneath Cassian's clinical precision lives a man who has learned to keep everything—especially his feelings—locked behind professional glass. The case is complex. The cave system is dangerous. And his partner is becoming impossible to ignore.

K9 handler Jonah Briggs has spent years reading people the way Cassian reads evidence—precisely, protectively, and never wrong. When their team descends on Missouri's limestone country, the investigation forces them into the kind of close quarters that make maintained distance feel less like professionalism and more like cowardice. Jonah's instincts aren't just tactical; they're personal. And every day beside Cassian makes denial harder to sustain.

Six victims. Two years of systematic murder. A corporate conspiracy using Missouri's ancient cave system as an industrial grave. As flash floods seal their investigation window, Cassian and Eli descend underground—only for an explosion to seal them inside. The killer is still moving. Living hostages are running out of time. And a single coded radio transmission may be the last message Cassian ever sends.

Months of careful distance dissolve somewhere between a near-fatal sinkhole slip and an embrace in a flooded limestone chamber. But surviving a case together doesn't resolve what exists between them—it only makes avoiding the question unconscionable. What happens when the evidence is undeniable and the only variable left is courage?

A slow-burn, forced-proximity MM romantic thriller featuring forensic science, cave rescues, and two men learning that the most dangerous evidence is the kind you find in yourself.