Dateline investigates the case of a young Fairfield, Ohio, woman, 21-year-old Katelyn Markham, who vanishes one summer night in 2011, prompting her community to conduct a massive search. When her skeletal remains are found in Indiana two years later, investigators question her friends and family to uncover her killer, but It takes 12 years and a detective with dogged determination.

A new father is found dead on the side of a road. Then the stabbing of a young woman leads police on a high speed chase. Could these two chilling murders be connected? Josh Mankiewicz reports.

In Humble, Texas, a frantic 911 caller, 16-year-old Keri Murphy, reports hearing her mother's screams after an intruder entered their home. When first responders arrive, they find Mary Ann Murphy dead after receiving more than 70 stab wounds. What happened on that dark summer night?

A monster storm had rolled into Canton, Massachusetts, and Karen Read's boyfriend, police officer John O'Keefe, was dead, his body discovered in front of another officer's house. Karen was charged with John's death. Was she to blame?

In Marietta, Georgia, a woman's murder shines a light on an unsolved mystery from years earlier. As the connection between the two cases becomes clear, a long-hidden truth surfaces. Could a master manipulator be behind both crimes? Andrea Canning reports.