Saturday mornings were usually pancake days at the Findley residence, and while Cadence would have slept past eight if she had been home, Cass was one to get up early and help her dad make a mess in the kitchen. Despite her own exhaustion from being up most of the night, Cadence was up bright and early to give her little sister a call and try to explain what she had seen the night before.

Cadence didn’t use FaceTime because she looked like grim death. Her plan was to talk to her sister briefly and then go back to sleep. She was hopeful that her sibling would comply. The phone...