Sunk in chronic lethargy, "I" follow my mother on a walk along Namdaecheon stream and recall an old elementary school assignment: catch a planarian. I never found one back then; I just played on the trampoline ("bang-bang") nearby. An unsolved mystery remained: do planarians really live in Namdaecheon? This film is the story of a middle-aged woman with a new ADHD diagnosis who, in trying to find the answer, tumbles down a rabbit hole of planarian obsession.​