Echo, Shelly Siren’s best friend, is doing tail flips because she’s going to see the hottest boy band around—The Rays! It’s her classmate Pearl’s birthday, and the Rays are going to perform at her exclusive party. Troublemaker Pearl has invited just about everyone—everyone, that is, except Shelly! Shelly urges Echo to go anyway, but Echo doesn’t want to leave her friend out of the exciting celebration…so Shelly hatches a plan to make sure Echo sees her favorite group. And when the Rays do come to town (amidst plenty of under-the-sea, boy band drama), Echo returns the favor so that Shelly is included in the festivities—in the most unexpected of ways!