Three weeks after the events of Split, David Dunn (Bruce Willis) works with his now adult son Joseph in using his superhuman abilities to protect people from criminals under a new alias known as “The Overseer”. David learns from Joseph that Kevin Wendell Crumb (James McAvoy), who suffers from dissociative identity disorder which provides his moniker “The Horde”, has a group of cheerleaders up in a warehouse. David goes to free them but encounters one of Kevin’s personalities known as “The Beast,” and the ensuing fight spills out into the streets.