Arang & the Magistrate S01E05 - The Only Clue To Find Mother

Eun Oh tells Arang that the hairpin she had was his mothers. They both decide to join forces in order to find out about her death and his mothers whereabouts. While Arang is sleeping, Lord Choi's son disguises himself and stabs Arang in the heart with a knife, taking her to a mountain (Eun Oh's mother is the one who orders Lord Choi's son to kill young girls with pure souls, and bring them to her). Arang wakes up and escapes from them.