According to Comicbookmovie, a reliable source who has shared the plot from the upcoming ‘Joker’ movie. Below is the reported plot according to comicbookmovie:
“It’s said that Joker takes place in Gotham City in 1981, and the iconic DC Comics location is at its lowest point with a crime wave and garbage strike leaving it dirtier and more dangerous than ever.
Arthur Fleck is just a nobody who works as a clown for a talent booking agency and he has a social worker keeping a close eye on him because he has some serious mental health issues. Those include an uncontrollable habit of laughing whenever he’s nervous, something which doesn’t help with his desire to become a stand-up comic.
He’s also a caretaker for his mother, a former housekeeper for the Wayne family…
As expected, Thomas Wayne is running to become the new Mayor of Gotham City, and he promises to clean up the city (both literally and figuratively). He’s a good man but has been ignoring his former employee, as Fleck’s mother has spent months trying to contact him to no avail.
She’s as deranged as her son, though, so it’s hardly a surprise that he’s not reading her correspondence. “