Inner Demons follows four teenagers – Carson, Paige, Brian, and Taylor – who decide to spend their summer at the beach on a camping trip. While officially the reason for their trip is to disseminate the ashes of Carson's grandfather, the real motivation behind the trip is for the group to lose their virginity.
Things take a dark turn when the group encounters a mysterious man who gives them a bag of drugs, promising them the "ultimate high." Despite initial reservations, the group decides to take the drugs, which sends them into a hallucinogenic state.
As the trip progresses, the teenagers begin to experience terrifying visions and vivid nightmares that seem to reflect their deepest fears and desires. It soon becomes apparent that the drugs they took have opened a portal to a terrifying demonic realm that preys on their innermost demons.
As the teens struggle to maintain their grip on reality, they must confront their inner demons in order to survive. With tensions running high and dark secrets threatening to tear them apart, the group realizes that their desire for a summer of pleasure has turned into a battle for their souls.