It is the year 1888, a serial killer, has been targeting London, and there is a set panic:

So far, 5 women, who were all prostitutes, have been brutally butchered in the street, and the detectives and police don't know who did it.

Since they don't know who did it, they name the perpetrator Jack the Ripper because they like ripping up their victim.

Meanwhile, Jack, or his real name is Jake Castello, is Jack the Ripper, but no one suspects him. He's charismatic, charming, and funny, which he uses to lure his victims in.