While not a traditional whodunit, "Flatliners (2017)" earns its place among the best mystery movies due to its exploration of the unknowable: what lies beyond death. The film masterfully unravels a complex web of secrets and guilt as medical students, driven by scientific curiosity, deliberately induce near-death experiences. The central mystery revolves around the increasingly bizarre and terrifying consequences they face after their brief journeys to the other side, forcing them to confront their past transgressions and question the very fabric of reality. The escalating tension and psychological thriller elements create a compelling mystery that keeps viewers guessing about the true nature of their experiences and the malevolent force seemingly unleashed by their experiments. The film's mystery is not simply about solving a crime, but about understanding the nature of the human psyche and the potential repercussions of tampering with the unknown. Each character's personal demons manifest in increasingly unsettling ways, creating a puzzle that the audience must piece together alongside the protagonists. The ambiguity surrounding the supernatural elements and the blurred lines between reality and hallucination contribute to a pervasive sense of unease and suspense. By intertwining the medical drama with elements of psychological horror and a central, existential question about life after death, "Flatliners (2017)" delivers a unique and thought-provoking mystery that lingers long after the credits roll.