It becomes clear that "Dennis" is in reality Kevin Wendell Crumb, a man diagnosed with dissociative identity disorder (DID) rooted in his history of childhood abuse and abandonment.

"The Beast" savagely feeds upon and kills Claire and Marcia before approaching Casey, but she calls out Kevin's full name, which brings forth his original personality.

Upon learning of the situation and realizing that he has not been in control of his own body for two years, the horrified Kevin begs Casey to kill him with a shotgun he has hidden.

He moves closer to murder her, but stops when he sees scars across her abdomen and chest, which are related to her abuse from her uncle and legal guardian, John, both before and after her father's death.

At the Silk City Diner, several patrons watch a news report on "The Beast's" crimes, with the correspondent mentioning that his numerous alters have earned him the nickname "The Horde".

"[7] On October 2, 2015, James McAvoy was cast in the film to play the lead, replacing Joaquin Phoenix, who had left the project a few weeks before it began shooting.

[8][9] On October 12, 2015, Anya Taylor-Joy, Betty Buckley, Jessica Sula, and Haley Lu Richardson were added to the cast.

[16] During post-production, Sterling K. Brown's role as Shaw, Dr. Fletcher's neighbor, was cut from the film, as Shyamalan felt that his scenes were ultimately unnecessary.

The website's critical consensus reads: "Split serves as a dramatic tour de force for James McAvoy in multiple roles – and finds writer-director M. Night Shyamalan returning resoundingly to thrilling form.

[34] Jordan Hoffman of The Guardian gave the film four stars out of five, stating it to be a "masterful blend of Hitchcock, horror and therapy session".

[35] Also writing for The Guardian, Steve Rose had strong praise for McAvoy, opining that the actor "does a fine and fearless job of selling his character's varied personae".

"[36] Christy Lemire, writing for RogerEbert.com, gave the film a score of 3 out of 4 stars, describing it as "an exciting return to form" and "a thrilling reminder of what a technical master [Shyamalan] can be.

"[37] Kate Muir of The Times gave the film a score of 3 stars out of 5, writing that it "is full of plot holes, but McAvoy's joyful and menacingly lunatic performance papers over most of them.

"[38] David Edelstein of New York magazine was critical of the film, writing: "Shyamalan has returned to what he loves to do: use cheap horror tropes to create his own harebrained mythos", and added: "Though Shyamalan doesn't use a lot of blood in Split — there's barely any — his framing sexualizes the torture of the other two teenage girls in a way I found reprehensible.

"[39] Anthony Lane of The New Yorker described the film as "an old-fashioned exploitation flick—part of a depleted and degrading genre that not even M. Night Shyamalan, the writer and director of Split, can redeem.

[44] "You are going to upset and potentially exacerbate symptoms in thousands of people who are already suffering," psychiatrist Dr. Garrett Marie Deckel, a DID specialist at Mount Sinai's Icahn School of Medicine, said immediately after seeing the film.

Movies tend to portray only "the most extreme aspects" of the disorder, which, she said, can misrepresent a form of mental ill-health that is not well understood by the lay public, and even some psychiatrists.

In an open letter to Shyamalan, several activists said that "Split represents yet another gross parody of us based on fear, ignorance, and sensationalism, only much worse.

[55] Disney, which produced Unbreakable through its Touchstone Pictures division, was expected to be a production partner and have financial participation with Universal for the sequel.

[63] The cast included the return of Bruce Willis from both previous films, Samuel L. Jackson, Spencer Treat Clark, and Charlayne Woodard from Unbreakable, and James McAvoy and Anya Taylor-Joy from Split, all reprising their roles.

[66] It was reported the new film would focus on Dunn (Willis) chasing down Crumb (McAvoy) in his Beast persona, all the while being embroiled in a plot orchestrated by Price (Jackson).