Gigi Stewart and her best friend, Finley, are always together. And everything they do, they document on the Wall, their collage in Gigi's room that holds layers and layers of memories—from movie tickets to magazine ads to embarrassing baby photos—and they never stop adding to it.

But when Gigi suggests they start planning their annual joint birthday blowout, Finn just doesn't seem that into it. She's more interested in extra soccer practice and hanging with the girls from the varsity team than choosing a party theme or going to cooking class or sleepovers with Gigi.

Though she tells herself it's no big deal, Gigi can't help but be hurt. And she's even more hurt when she discovers that Finn's been lying about what she's been doing and who she's been hanging out with instead of her.

Gigi thought she and Finn would be friends forever—but what happens when "forever" comes to an end?