A group of four friends find themselves in peril when they agree to give a ride to a stranded woman, hoping to do a good deed. However, their goodwill takes a dark turn as they are abducted and wake up in a locked room with several other captives. A disturbing video informs them that they are part of a twisted experiment: everyone in the room has been fitted with a device at the base of their skulls that can only be removed once they collectively produce a specified amount of pain-based endorphins. If they fail to meet the quota within the time limit, the devices will kill them.

With no choice but to comply, the group is forced to inflict pain on themselves and each other, revealing deep-seated fears and testing their relationships to the breaking point. As the hours tick by, alliances shift and crumble, exposing the vicious lengths some captives will go to ensure their survival. The situation grows increasingly desperate as they confront not only the physical agony they must endure but also the psychological torment of the horrific dehumanization. Tensions mount as trust becomes a rare commodity and the lurking suspicion that there might be more to the seemingly random selection process heightens their paranoia. The grim realization dawns that escape may only be achievable at an unthinkable cost.