In a society that reveres monster hunters, Cheon Haesun, ostracized for his peculiar appearance, faces a double blow when he learns of his terminal illness amidst a monster onslaught in his community. Saved by his sister's selfless act, Haesun defies death and awakens as a Poisoner, a unique hunter blessed with venomous curative powers. Yet, as he grapples with his newfound abilities, the question looms: Can his toxic talents heal his affliction and pave the way to the ordinary life he has long yearned for?