The Mob Squad are the greatest heroes the town of Cornucopia has produced since it was founded: Mal the bold, Lenna the strong, Tok the wise, and Chug the steadfast. And Jarro, who's renounced his bullying ways to reveal a truly kind heart. Together they've journeyed across the Overworld, delved into the Nether, and saved the day for Cornucopia again and again.

So why can't they get any respect from the adults who run the town? The only one who understands is Nan, Mal's great-great-great-grandmother, who trained them to be as resourceful and adventurous as she was in her day.

So when Nan gets sick and isn't getting any better, the kids refuse to just sit by and do nothing. There's something out there that can help her--an enchanted golden apple that can cure just about anything. And the Mob Squad will stop at nothing to get it.

But as they venture outside the walls of Cornucopia, they aren't counting on being followed. The kids soon discover a mysterious foe whose motives are as unknown as the face they hide behind a creeper's head. If the Mob Squad wants to rescue Nan, they're going to have to save themselves first.