Fifth grade is not for amateurs, according to Liam. Luckily, he knows that being more than one-third nerd is not cool. Liam lives in the Bay area near San Francisco with his mom and two younger sisters. Dakota is fascinated by science and has a big personality but struggles to make friends; Izzy, a child with Down syndrome, makes friends easily and notices things that go past everyone else. Dad lives across town, but he's over a lot. And then there's Cupcake, their lovable German shepherd, who guards their basement apartment.
Recently, Cupcake has a problem—she's peeing in the house. The kids need to make enough money to take her to the vet before their landlord upstairs finds out. And Mom and Dad have said if Cupcake doesn't stop, they will find her a new home. But the kids will never let Cupcake go. Can they save her?