Secret in the Mist - S1.E4

Erin hears that Shaju's older sister has been engaged. But while eating a rice cake, Soju, Shaju's sister, suddenly falls ill. Soh-yon diagnoses Soju's illness as "Mock milkweed poisoning" a poisonous plant that was mistaken as a plant used in the cakes. Soh-yon decides to ask her clan, the Mist People, for the medicine.