Even though her family calls her Emma Bemma, Emma knows she is really just a dilEmma because she is just medium. That's because she's the middle kid between her two brothers, who everyone calls Big and Little. Big thinks he's the coolest kid on the planet now that he's 10. And everyone thinks Little is just adorable even when he picks his nose and eats it! Ugh! What's a middle child to do?

Sometimes Emma feels like the only one who understands her is her Japanese fighting fish, Star, whose tank is stuck in the middle of his two brothers. And as usual, Emma has to ride in the middle seat as her family heads out on a weeklong beach vacation with friends, where being just medium will only get worse! Then Emma has an idea. What if she could get out of being in the middle by taking on a new role? What if she acted BIG? Or even bigger than that? Will things go as planned? Or will she have another huge dilEmma?