Season synopsis
Contains spoilers for this season and earlier seasons.
Moon Gang-tae works as a psychiatric hospital caretaker, arranging his life around his older brother Sang-tae, whose fear of butterflies is tied to their mother's murder. Their routine changes when author Ko Moon-young returns to their hometown and draws both brothers into her orbit. Gang-tae and Moon-young form a difficult bond while helping patients face grief, abuse and guilt; Sang-tae begins to claim room for his own interests instead of relying on Gang-tae to make every decision.
A butterfly image links their past to Moon-young’s mother, Do Hui-jae, whom Gang-tae suspects of murdering his mother. Sang-tae’s recovered memory identifies the killer by the butterfly on her jacket; evidence later reveals Hui-jae is alive and working as the hospital’s head nurse under another identity. She tries to control Moon-young and attack the family, but Sang-tae knocks her unconscious with a book, saving Gang-tae and Moon-young. Moon-young rejects her mother’s claim over her, and Hui-jae is arrested. The revelation tests Gang-tae and Moon-young’s trust, while Sang-tae’s growing independence lets him face the danger alongside them instead of being treated as someone who must always be protected.
Moon-young publishes a book about the three finding courage to recover their “stolen faces.” At the launch, she and Sang-tae argue over who will read it, then take turns until their bickering interrupts the event. Friends and patients gather around them. Director Oh gives Sang-tae a camper van for his mural, and the trio set out together. Gang-tae and Moon-young affirm their love; Sang-tae decides to illustrate books for other authors and leaves with publisher Lee. Gang-tae lets his brother choose that path, and they part warmly before he continues travelling with Moon-young.