After months away, Emily returns to London and to a family on the verge of disintegration. She spends nights in cramped bars, drinking and smoking with her beautiful but damaged boyfriend Tom and his friends. It is a lifestyle the leaves her feeling directionless and jaded. In her search to believe in something or someone, she finds herself irresistibly drawn to Simon, Toms complex and charming cousin. But Simon is married, and as he and Emily become closer and the summer draws to an end they are forced to make decisions that will have a devastating effect on both families.