Investigators walked into a mystery that would turn their world upside down… Watch tonight at 9/8c on a 2-hour Dateline Weekend Mystery on NBC. | Dateline NBC

Tonight on a new Dateline, the latest chapter in this hair-raising tale, featuring new evidence, explosive testimony and the prosecution's new star witness. Watch at 9/8c on NBC. | Dateline NBC

A medical mystery was about to turn into a full-on police investigation… Tonight on an all-new Dateline at 10/9c on NBC. | Dateline NBC

Two unsolved murders became four... The second Dateline Weekend Mystery at 9/8c. | Dateline NBC

On the morning of July 11, 2006, Mary Cooper and her daughter Susanna Stodden were murdered on a trail northeast of Seattle, Washington. More than 12 years later, their murders remain unsolved. David Stodden, Mary’s husband and Susanna’s father, tells Dateline about his search for justice. | Dateline NBC

Thirty-two years ago this month, a series of murders began near and along Virginia’s Colonial Parkway. When it was over, four couples were dead at the hand of what authorities believe could be a serial killer. The crimes were dubbed “The Colonial Parkway Murders.” | Dateline NBC

More on John and Lauren's Hidden True Crime podcast | Dateline NBC

It’s a story about a red-hot Texas passion and a bitter feud... And tonight at 10/9c on Dateline, there’s a whole new chapter. | Dateline NBC