In 1981, party clown and aspiring stand-up comedian Arthur Fleck lives with his mother, Penny, in Gotham City. Gotham is rife with crime and unemployment, leaving segments of the population disenfranchised and impoverished. Arthur suffers from a disorder that causes him to laugh at inappropriate times, and depends on social services for medication. After a gang attacks him in an alley, Arthur's co-worker, Randall, lends him a gun. Arthur invites his neighbor, single mother Sophie, to his stand-up comedy show, and they begin dating.
