One of the most famous unsolved mysteries of all time is the identity of Jack the Ripper, a notorious serial killer that terrorized London’s East End neighborhood in 1888, Biography.com reports. Despite investigations of the five murders, the identity and motive of “Jack” are still unknown. Theories on the real identity of the murderer are just as inventive. Some theorists claim a famous Victorian painter, Walter Sickert, is guilty, while others say it could have been Queen Victoria’s grandson. Still, there were more than 100 potential suspects. More recent investigations point to a Polish immigrant as a highly possible suspect, but there are disputes about DNA results, according to Biography.com. That’s why so many movies, TV shows, and books on the Ripper always pop up.