The Plague Sower

S1 E15: A sudden, mysterious bleeding illness quickly spreads through Trinity, causing death and devastation, as well as the arrival of a new doctor. As the townspeople fall victim to the plague, Matt suffers a breakdown and Lucas turns to Dr. Peele for help. After a romantic encounter with Lucas, Gail is suddenly stricken. Meanwhile, Caleb appears to be immune to the epidemic's bloody "evil force," as Merlyn hovers and watches the horror with dispassion.