Netflix's true crime series, "Unsolved Mysteries," has returned for a fourth season and it kicks off with the story of Jack the Ripper.
The Ripper has never been formally identified, but there are plenty of theories about who could have murdered at least five women in London's east end in 1888, which have captivated true crime fans for decades.
The gruesome mystery has been turned into various TV shows and movies — including Johnny Depp's "From Hell," as well as the "Edge of Sanity," "Ripper Street," and "Whitechapel," which have helped keep interest in the mystery alive.
The killer disappeared after murdering his final victim, a sex worker called Mary Jane Kelly, on November 9, 1888. Here are the four main suspects examined by "Unsolved Mysteries."