The snow fell in thick, heavy flakes as Dr. Elias Voss’s car sputtered to a stop on the main street of Blackpine. The town looked like a postcard come to life—weathered wooden houses with smoke curling from chimneys, a general store with a faded “Open” sign in the window, and a clock tower that chimed once, its sound echoing through the empty streets. But beneath the picturesque surface, there was a tension in the air, like the quiet before a storm.

Elias turned off the engine and ...