My neighbors loud arguments led to a shocking discovery

My apartment building has pretty thin walls. I've gotten used to hearing my neighbors. Especially the couple next door. They argue a lot. Mostly about small stuff. Like whose turn it is to take out the trash. Or who left the lights on. It's usually just background noise for me. But a couple weeks ago on a Wednesday evening the argument was really loud. It sounded serious. I could hear yelling and crying. I was worried for a bit but it eventually quieted down. The next morning I saw the wife leaving for work like usual. She looked really upset though. Her eyes were puffy. I thought maybe they had a really bad...