Investigators piece together murder mysteries and seek insight into the victims' lives - and sometimes into their darkest secrets.

In the wake of a family tragedy, a strong-willed teenager and her grieving stepfather volunteer to help a mysterious tech company evaluate its new A.I. operating system.

The crew of USS Titan find themselves on the brink of WWIII with Russia when a naked stowaway appears in one of their torpedo tubes. Captain Banks fears she may be Russian, but she's something far more dangerous.

The search for Harold Heaven, who mysteriously disappeared from his remote cabin in Ontario, Canada, in the winter of 1934.

Police officers, paramedics and other first responders reveal their terrifying true tales of encounters with the paranormal while on duty.