When Abby signs up for a DNA service, it's mainly to give her friend and secret love interest, Leo, a nudge. After all, she knows who she is already: Avid photographer. Injury-prone tree climber. Best friend to Leo and Connie...although ever since the B.E.I. (Big Embarrassing Incident) with Leo, things have been awkward on that front. But she didn't know she's a younger sister. When the DNA service reveals Abby has a secret sister, shimmery-haired Instagram star Savannah Tully, it's hard to believe they're from the same planet, never mind the same parents - especially considering Savannah, queen of green smoothies, is only a year and a half older than Abby herself. The logical course of action? Meet up at summer camp (obviously) and figure out why Abby's parents gave Savvy up for adoption.