After a supernatural encounter, Matt Zimmer feels undeniably drawn to a radio broadcast it seems only he can hear. He is subsequently haunted by the voices in the broadcast and becomes obsessed with discovering where the radio signal originates, putting severe strain on his business and family. By mounting antennas to his truck, Matt follows the signal across the state of Texas and soon meets three other people who have the same story and experience. They quickly learn they were brought together by the broadcast for a reason. The mystery unravels as they search the small Texas town of Sulpher Springs and discover a disturbing secret. Their mission: to protect what could be the key to the end of the world. But an evil stands in their way as they fight off insurmountable odds. Sacrifices will be made and lives will be lost, in a shocking finale that may lead to The Last Tomorrow.