The kids at school call her rag girl because she hides under layers of oversized clothing, but she calls herself Ophelia. She hardly speaks to anyone — until one day a visiting author comes to give a talk in the school library. The writer speaks about what it means to create art, and at the end of her talk, she thanks Ophelia for asking the first question by giving her a blue notebook with her address on it.
Ophelia starts to write to the author in the notebook — letters that become a kind of lifeline. The idea that someone, somewhere, might care, is enough for her to keep writing, an escape from her real life. By day she goes to school and works at the dollar store before returning home to her mother, a former addict who once had to put her daughter in care. At night she creates graffiti around town, leaving little broken hearts as her tag.
One night she finds an abandoned building that she decides to use as her workshop, where she can make larger-than-life art. When she finds that a classmate, an overweight boy named Ulysses, is also using the space to repair an old van, the two form an uneasy truce, with a chalk line drawn down the middle to mark their separate territories. As time passes, Ophelia and Ulysses forge a fraught but growing friendship, but their cocooned existence cannot last forever. One night, intruders invade their sanctuary, and their shared bond and individual strength are sorely tested.