Lorenzo Orsini (Jonathan Barrett), despite wearing the killer clown getup, wasn’t the one who murdered all except Kate (Sarah Lassez) and George (James Duval) in the theatre, and he also wasn’t the one who killed Kate’s mother Lorraine (Vicki Marentette), since they were engaged and he was Kate’s biological father. The real murderer is Caruthers (Christopher Plummer), the theatre owner. He wanted Kate’s mother to be his love, but Kate chose Orsini over him. Angered by this rejection, he killed her and then framed Orsini for it, and then kept him trapped in the opera house when the police officially pinned the murder on him and he didn’t want to go to jail.
Caruthers kills Orsini when the latter finally stands up to him, and then he ties up Kate for a personal opera play, acting like she was Lorraine, with all of her dead friends as the audience. When he goes backstage to turn the soundtrack on, he encounters George, wearing the clown getup after Orsini pulled him aside and explained everything to him. They fight, but George gets knocked out. However, the fight buys Kate enough time to loosen her restraints a little, and some time after Caruthers returns to her, she frees herself and stabs him in the eye with a screwdriver. While he is reeling in pain, she opens a trapdoor below him, and he gets impaled on a rack of prop spears.
Kate and a revived George hug and then escape the theatre.
Thanks, Tornado Dragon!