A killer is on the loose in the City of Sorcery, and Damon Wolfhard, second year resident at Golden Willow hospital, fears it might be him. Damon keeps having dreams about murders that happen in the city and waking up covered in someone else's blood. Then his father falls deathly ill while visiting the hospital creating new worries for him. As his father's health grows worse, and the killings in the city become more frequent, Damon learns the real truth about his family's tragedy. Damon enlists his friends' help in a race against time to stop the Full Moon Killer, and despite all his efforts otherwise will end with one of his family members dead.