Act as an experienced screenwriter specializing in psychological thrillers with a background in crafting unreliable narrators. Develop a gripping screenplay outline where the protagonist's perception of reality is constantly in question. The story should take place in [SETTING], involve a central mystery surrounding [EVENT], and feature a secondary character who may or may not be a figment of the protagonist's imagination. Use subtle visual and auditory cues to hint at the narrator's unreliability, such as [DETAIL 1], [DETAIL 2], and [DETAIL 3]. The tone should be unsettling yet immersive, leaving the audience questioning what is real until the final reveal.