Ivy arrived on the ragged edge of a storm. It was wet, wild, and humid in the Myakka boonies. At first, she simply sat there in the borrowed red Corolla, watching the windshield wipers dance back and forth. After a few minutes, she killed the car’s headlights, then the engine.

She pushed the driver’s door open and stepped out into the rain. The raging sky at her back was a beast in agony, swirling with bubbly clouds of ash and electric blue.

The house was painted white, a century-old wooden affair...