FX: The Series (1996)

S1E16 Gemini

After noticing unsettling parallels between a sci-fi film that Rollie is working on and a notorious unsolved murder case in Central Park, Leo becomes convinced that the film's director is the elusive serial killer from four years prior. He persuades Rollie to utilize special effects to extract a confession, but they quickly realize that the director suffers from a split personality. As his violent alter ego begins to emerge, it seems poised to strike again.