A whiz-kid inventor and his ragtag crew must save the world from aliens…againIt's unclear why Ferrous City is a "hotbed of alien activity," but Ethan Fairmount knows that he can't tell his parents about any of it-especially not about another potential alien attack just a few months after the last. And even as he turns to his friends instead, he still doesn't initially tell them the whole truth about his beloved and now-missing guinea pig, Nugget. Ethan is scared and in over his head when he reaches out via walkie-talkie to the squad-his oldest friend, Kareem, inventive Fatima, creatively inclined Jodie, siblings RJ and Di (the latter of whom Ethan has a huge, not-so-secret crush on), and loyal new friend Juan Carlos. The narrative jumps right into the adventure as the ranks of aliens grow-both the good guys accompanying small, purple, six-eyed Cheese and the world-destroying reptilian light-thieves. Ethan eventually needs to add his big brothers to the hero squad, a move that draws attention to his habit of keeping secrets from those closest to him. Ultimately, the bumbling, one-dimensional alien villains who seemingly barely understand their own nefarious goals and technology stand no chance against an abundance of clever, sometimes snarky, and increasingly tight-knit young Black and brown humans and their alien companions. The path to a happy ending relies just as much on realizing how invaluable friendship is as it does on sheer luck.A solid trilogy closer for returning fans.(Science fiction. 8-12)