Maisie Fernandez has just about convinced herself that she does not care about her weight or her looks, or about only having one friend in Fort Collins High School (nerdy Owen Carpenter), but "Sienna", the internet profile she creates, is beautiful, skinny, and confident; the profile is part of her plan to humiliate the popular kids who bully and make fun of her, but suddenly the deception gets complicated--because the actual Sienna, the girl whose photos Maisie has been using, shows up in real life.