Hours of painstaking investigation and technological sleuthing had finally borne fruit. The police traced the ransom message to a small industrial building on the outskirts of town—a structure that had once belonged to Autumn’s family company before it went bankrupt years ago.

The irony wasn’t lost on Autumn. That her mother had chosen a place emblematic of their family’s collapse—both financially and emotionally—felt like a deliberate, bitter statement.

They had left the house with Evette and Aaron to stay behind. They wanted Autumn stay behind as well but she was adamant on seeing her babies.

As the police prepared their strategy, Autumn and Derek sat in the back of a...