As his Noggles Ceremony approaches, a young Nouns named Gi Tian envisions a future where he's chosen for his dream job as a Rover.

While Gi accompanies his father to work, the tyrannical Leader Blunt unveils a new kind of Noggles that will usher in an age of servitude unlike any that Nouns have ever seen.

With his father taken, Gi and Mara try to lay low and adjust to their new circumstances. But when Leader Blunt's goons track them down, a mysterious new figure comes to their aid.

Gi and Mara are thrust into a hidden underground world led by Mrs. Waxman, racing through secret tunnels beneath Blus. Emerging in a mysterious base, they discover the truth.