The document provides a detailed summary of the plot of the film Split. It describes the main characters of Casey Cooke, Claire Benoit, and Marcia and how the three girls are kidnapped by Kevin Wendell Crumb who has dissociative identity disorder and 23 personalities, including the dangerous personality known as "The Beast". The summary then outlines Casey's journey to try and escape with the other girls and ultimately defeat The Beast with the help of clues from the psychiatrist. It concludes with Casey reporting her uncle to police for past abuse.