The dip appeared on a Tuesday, between the kitchen and the hallway, a soft depression in the hardwood about the size of a welcome mat. Sandra noticed it when her coffee tilted in her mug on the way to the table. She mentioned it at breakfast. "There's a dip," she said. "Hm," said her husband, Paul, not looking up. "I'll take a look," he said, in the tone he used when he would not take a look. She stepped around it on her way out the door. It was easy enough to step around. By Thursday, it was deeper.