A psychiatrist who previously treated Leslie. He interrupts the documentary to reveal that Leslie is an ordinary, mentally unstable man named Leslie Mancuso, shattering his slasher persona. He survives the attack.
Halloran has clinical knowledge that undermines Leslie's constructed identity.
Doc Halloran states that he previously treated Leslie in Reno, Nevada, and identifies him as Leslie Mancuso rather than a legendary killer.
Halloran's revelation forces Taylor to reassess the subject she has been documenting.
Taylor hears Halloran's allegation about Leslie and confronts Leslie about it before deciding to continue filming.