The film tells the story that Arthur is a young man. He lives with his sick mother Penny and takes care of her. Arthur is a clown in Gotham. Arthur has been suffering from mental illness, and some of his behaviors are beyond his control, which makes him a laughing stock from time to time, and these taunts are very inappropriate.

Arthur has no real friends and no outlet to stabilize negative emotions. He has been paying attention to the lives of two people, one is TV talk show host Murray, and the other is a young single lady Sophie who lives in Arthur's apartment. He expressed some short-term goodwill to him, which made Arthur enter the stand-up comic industry.

Arthur, a very introverted young man with some mental problems. He lives in a shabby apartment with his sick mother Penny. While taking care of my mother, I make a living as a clown and dream of becoming a comedian. Finally, he couldn't stand it any longer and went crazy.