In December 1998, police in Pleasant Prairie, Wis., were called to the Lake Shore Drive home of Mark and Julie Jensen. Inside, Mark had found his wife's body lying in her bed. Initially, investigators thought suicide was a strong possibility. But a letter written by Julie before her death pointed police in a different direction. Was the husband somehow involved in his wife's death, as the letter hints? Or did Julie poison herself and pen the letter to implicate Mark in a twisted plot gone wrong, as his parents allege? Erin Moriarty reports for 48 Hours Mystery.