Montana and her sister, Arizona, are named after the mountainous states their mother left them for. But Montana is a New York City girl through and through, and as the city heats up, she's stepping into the most intense summer of her life. Her father is distracted by yet another divorce, and she's growing apart from her sister. Then she meets wild, bold Karissa, who encourages Montana to live in Technicolor and chase new experiences. But the more of her own secrets Karissa reveals, the more Montana has to wonder if Karissa's someone she can really trust. In the midst of her uncertainty, Montana finds a beautiful distraction in Bernardo. He's serious but spontaneous, and he looks at Montana in the way she wants to be seen. For the first time, Montana understands how you can become both lost and found in somebody else. But when that love becomes everything, where does it leave the rest of her imperfect life?