In December 2020, a team of civilian codebreaker broke one of the unknown killer's messages after 51 years. Are we now closer to finally finding out who he is?

In very rare instances, people who suspect their fathers, brothers or other family members are long-sought serial killers are dead right and help authorities solve a notorious cold case. But far more often, they pester police with circumstantial evidence backing up wild theories.

Historian Hallie Rubenhold, author of the book, 'The Five: The Untold Lives of the Women Killed by Jack the Ripper,' believes the victims of Jack the Ripper weren't all sex workers—they were just women who were asleep.

Peter Vronsky, author and investigative historian, speaks with us about ancient killers, the influence of technology on crime and how, in 100 years, the Long Island Serial Killer could be the new Jack the Ripper.

Killers who leave notes at crime scenes or mail missives to police and the press take a big risk. Read stories and watch videos about eight murderers who just had to put it in writing.