Set in the 1980s, the movie tells the origin story of the Joker. After failing to find success as a stand-up comedian and feeling ignored by society, Arthur Fleck wanders around in Gotham City while dressed up as a clown, encountering violent thugs. As he slowly descends into madness, he starts causing chaos and mayhem in the city, transforming into the iconic criminal mastermind known to many as the Joker.