Horrifying Secret takes place after her sister Melanie mysteriously disappears, Clover and her friends decide to go into a valley where she last saw her sister to find answers. When they stumble into an abandoned building, they are followed by a masked killer and are horrifically murdered one by one... until they wake up to find themselves back in the first evening. Trapped in a mysterious time loop, they are forced to relive the nightmare every night, but each time they face new threats and different, increasingly terrifying ways to die. As hope gradually fades, the group realizes they only have 13 lives left before disappearing forever. The only way to escape is to survive until dawn.