Karen McDonough of Quincy, Mass., was enjoying her tea one morning in the dining room when she saw something odd outside her window: a group of people gathering on her lawn. A man with a clipboard told her that her home no longer belonged to her. It didn't matter that she'd been paying her mortgage for 17 years and was current on it. She was a nurse with a good job and had raised her kids there. But this was a foreclosure sale, and she was going to lose her house. McDonough had fallen victim to what's called a zombie second mortgage. Homeowners think these loans are long dead. B...