Adult student Karin is curious about kissing. One night, she spots a man asleep across from her in an otherwise empty train and impulsively kisses him. She returns night after night to steal more kisses, until he wakes up in the middle of one and an awkward silence falls between them. Their eyes meet, their lips come together again, and soon they cannot stop. They press against each other and have sex in the deserted car. After both miss their stops, they get off at an unfamiliar station, check into a hotel, and spend the rest of the night kissing and craving each other's bodies.