There is a specific kind of blindness that infects a marriage when you trust someone completely. You stop looking for the cracks in the foundation because you assume the house is solid. For ten years, David and I had a beautiful, boring, perfectly solid marriage.

Or so I thought.

Three years ago, David started developing a strange, unbreakable routine. Every single Friday, right after he finished his shift as a structural engineer, he would drive across town to my older sister Karen’s house. When I first asked him about it, he brushed it off casually.

“Karen’s old farmhouse has terrible plumbing,” he had said, tossing his keys on the counter. “Her kitchen sink keeps backing up. You know she can’t afford a plumber on a teacher’s salary, so I’ve been going over to snake the drain and patch the pipes.”