Mallory kicked the snow off her boots and headed inside, noticing the mess they had left. So, she folded the blankets and set them on the floor beside the couch, out of the way, and slid the coffee table back into place. But before she washed their coffee cups, she decided to go exploring. She hated to snoop in other people’s homes, but she was starting to think of it almost as hers. She just hoped that the owners didn’t care that they snooped through their stuff.

Downstairs was two bedrooms and, of course, the bathroom between them. Then she headed upstairs and there were three bedrooms. Mallory went into...