Michigan mom Renee Pagel was found stabbed more than 50 times in her home on Aug. 5, 2006, just days after she donated one of her kidney's to the father of one of her nursing students. 

They seemed to have the perfect marriage, until one of them ended up dead.

Thad Harper's brutal death would unravel dark secrets and a stunning betrayal.

The wounds California nurse Sherri Rasmussen suffered in her final moments of life were "extensive and disturbing," but it would take more than two decades to reveal the surprising killer.