Phillip is a wealthy quadriplegic who needs a caretaker to help him with his day-to-day routine in his New York penthouse. He decides to hire Dell, a struggling parolee who's trying to reconnect with his ex and his young son. Despite coming from two different worlds, an unlikely friendship starts to blossom.

Though Kevin has evidenced 23 personalities to his trusted psychiatrist, Dr. Fletcher, there remains one still submerged who is set to materialize and dominate all the others. Compelled to abduct three teenage girls led by the willful, observant Casey, Kevin reaches a war for survival among all of those contained within him — as well as everyone around him — as the walls between his compartments shatter apart.