You have a boyfriend, but is your eye on someone else? And is it possibly his older sister? Rosemarie (Rose), has what she thinks is the perfect life. She goes to school, parties, and hangs out with her best friend, Caroline, all the time. Oh, and her boyfriend Lucas. Until one day he randomly asks her if she wants to come over and meet his parents. She's wondering why he's asking her now since they've been together for 5 years. But everything changes when she sees Harper... Lucas' older sister. Rose has never felt this way towards a girl before and especially not towards her boyfriends sister. This isn't right, right? Wrong. It's never wrong to love His Sister.

After a summer that changed everything, Lark and Sophie find themselves on opposite sides of a fragile friendship. Torn between loyalty to her boyfriend Liam and the undeniable spark with his sister, Sophie is drowning in secrets.