Contains spoilers for this episode and earlier episodes.
The butterfly on Sang-tae's mural sends Moon-young away in tears and leaves Gang-tae trying to reassure his brother. CCTV identifies Head Nurse Park as the person who painted it. The discovery exposes her as Do Hui-jae, Moon-young's mother, and flashbacks show her revealing herself to Dae-hwan before his death. She has been watching him and interfering with the people around her daughter. Gang-tae tells Moon-young that the nurse is her mother and refuses to treat Moon-young as responsible for the murder. Moon-young is horrified and tries to send him away, afraid that staying together places the brothers in danger. He holds her as she cries.
Sang-tae believes Moon-young is ill and brings her porridge, staying with her while she struggles to apologize. Gang-tae also asks his brother for comfort instead of pretending that he is unafraid. A package containing The Hand, The Monkfish arrives with a message from Hui-jae about rejecting failure. Moon-young responds by arranging news of her mother's unpublished manuscript, hoping to draw her out. Sang-in tries to keep Moon-young from walking into the confrontation. Hui-jae instead approaches Sang-tae, who still trusts her as the head nurse. She uses his phone to summon Gang-tae to the mansion. He arrives to find his brother unconscious and Hui-jae waiting, while Moon-young breaks away from Sang-in and runs toward the house.