For sixteen-year-old Ruby, GCSEs are over and summer has just begun, so that means hanging out with her BFFs in the park on their roller skates and having fun. She didn't expect it to mean signing up to run a 5k race for sporty sixth-formers. Because Ruby is NOT sporty. But she really needs to prove her mean brother and even meaner PE teacher wrong about what a fat girl can do. When Ruby starts to train, she doesn't expect that she would need help - nor that she would find it in the cute boy who has just moved in next door. As the two jog through the long summer evenings in south London's parks together, with Ollie only seeing her at her sweatiest and most vulnerable, the last thing she expected was that he might - like her. Or that she could allow herself to like him. But nothing this summer is working out like she expected.