Yeonnam-Dong's Smiley Laundromat is a place where the extraordinary stories of ordinary residents unfold. Situated at the heart of rapidly gentrifying district of Seoul, it's a haven of peace and reflection for many locals. And when a notebook is left behind there, it becomes a place that brings people together. One by one, customers start jotting down candid diary entries, opening their hearts and inviting acts of kindness from neighbours who were once just faces in the crowd. But there is a darker story behind the notebook, and before long the laundromat's regulars are teaming up to solve the mystery and put the world to rights.