In Portsmouth, VA, a father comes home to find his 16-year-old daughter stabbed to death. With DNA and fingerprints police hope for an open-and-shut case. However, the case still goes unsolved for months until a piece of gum points to an unlikely suspect.

When Austin York, Matt Self, Mark Barbosa and Rosa Barbosa are found dead in a McKinney, Texas, home, detectives embark on a three-year investigation. And just when it seems like the murders may never be solved, an eyewitness breaks the case wide open.

Karin Strom is discovered strangled to death in her home. When a suspect emerges, investigators don't have enough evidence for a conviction. It will take 26 years to ultimately prove their case, and the final outcome surprises everyone.

Ann Branson is found stabbed and beaten to death in her Kentucky home. There is little evidence at the crime scene and investigators struggle to find a motive. Ann's financial records provide the break authorities need to help catch the killer overseas.

Twenty-three-year-old Stephanie Bennett is brutally raped and murdered in her suburban Raleigh apartment. Investigators work the case for years but their leads go nowhere. A closer look at a peeping tom provides police the break they desperately need.