Yoon Jong-woo, a young aspiring writer from the countryside, moves to Seoul after landing an internship. Due to his tight financial situation, he is forced to rent a cheap, dilapidated dormitory-style room—known as a 'gosiwon'—called Eden Studio. There, he shares a narrow hallway and communal kitchen with a bizarre, unsettling collection of neighbors, including a sadistic dentist, a stuttering eccentric, and an aggressive gang leader. As Jong-woo struggles with the overwhelming stress of his new job and the claustrophobic environment, he gradually realizes that his neighbors are hiding a horrifying secret, and the gosiwon slowly transforms into a living hell that begins to unravel his sanity.