OK, so we've all heard of Jack the Ripper, right?
The murderer roamed the streets at night and was known for the grisly and almost surgical killings of a number of unsuspecting women.
However, some people believe Jack the Ripper wasn't a Jack at all, giving rise to a theory we'll call 'Jill the Ripper'.
Let's look at what we know.
We know that the serial killer murdered at least five women in the East End of London, specifically around Whitechapel, in 1888.
We know the police came in for some serious criticism for their inability to catch anyone, and the crimes remain unsolved to this very day.
On top of that, the gory nature of the killings - some victims had their reproductive organs removed, for example - captured the imagination of the world's press at the time.
However, few considered the idea that the murderer could be a woman, although there is a theory that suggests it as a distinct possibility.
The idea wasn't completely overlooked at the time. In fact, Detective Frederick Abberline, who was involved in the case at the time, was once said to have pondered: "Do you think that it could be a case not of Jack the Ripper but Jill the Ripper?"
His idea was based on the idea the murderer could have been a female midwife.
You see, at the time of Mary Jane Kelly's death - believed to have been the Ripper's fifth victim - she was thought to have been pregnant.
Kelly was extensively mutilated, and - unlike the others - killed at home.
A midwife would have had easy access to women's homes, and could have slipped away relatively unseen.
She would also have some of the knowledge shown in the mutilations performed on the victims, and would have attracted little attention if seen covered in blood.
It's not exactly concrete proof, but it's something worth thinking about.
The prime suspect for those who subscribe to this way of thinking is a woman called Mary Pearcey, who was convicted of her lover's wife and child and hanged in 1890.
She was also known to have used a method similar to the Ripper's killing style to commit those crimes.
So, could she have committed the other murders? We'll probably never know.Featured Image Credit: PA