Four college students are found stabbed to death in their home. Police say the suspect had studied the criminal mind. "48 Hours" correspondent Peter Van Sant reports. 

More than two decades after 48 HOURS correspondent Erin Moriarty began reporting on the case of a missing 12-year-old girl from Friendswood, Texas, there is finally a conclusion. What no one knew when Laura Smither first went missing in 1997 was that she had been the victim of a serial killer. William Reece would go on to murder three young women that same year before he was eventually identified by DNA. Moriarty, who has been on the trail since 1997, has the latest in "The Daughters Who Disappeared".