Sonic the Hedgehog 3: Up Against the Wall is a story book written for children ages four through eight. It is set in the same continuity as Sonic the Hedgehog television series.
The Freedom Fighters meet to discuss Dr. Robotnik's latest activity, and notice that he has been quiet lately. Sonic knows, though, that "Robotnik still has plenty of tricks up his metal sleeve." Just then, a loud "BOOM" sounds from the distance. Sonic goes to investigate the sound, and finds out that "a giant smoke-belching machine", the Wall-Upper 3000, is slamming metal wall sections into the ground.
The other Freedom Fighters meet up with Sonic, and they are all met by Dr. Robotnik and his assistant, Snively. Robotnik explains that he plans to build a wall around the entire Great Forest and put a dome over it to keep out sunlight and fresh air. The whole forest would eventually be destroyed. The Freedom Fighters are then attacked by Swat-Bots and Buzz Bombers, and retreat back to Knothole Village to create a plan to destroy Robotnik's machine.
Princess Sally proposes that they use a giant magnet Rotor made to magnetize the metal wall Robotnik was erecting. Robotnik's metal Swat-Bots would stick to the wall. Sonic also has Bunnie Rabbot paint fake scenery on a canvas to lure the Wall-Upper 3000 to where they want it to go.
Sonic, Antoine, and Sally pull a wagon full of Golden Rings to Robotnik and his machine. They have to work fast because the machine is making great progress in surrounding the Great Forest with a metal wall. Sonic tricks Robotnik into getting close to the wagon. Suddenly, Sonic whistles, signaling Rotor to come up out of the wagon with his giant magnet. The magnet pulls toward the wall and magnetizes it. Robotnik (because of his robotic arm) and all his Badniks are drawn to the wall. Sonic whistles again and Tails appears with Bunnie's fake scenery. He holds it in front of the Wall-Upper 3000's eyes, and lures the machine "over a cliff to its doom."
The Freedom Fighters return to Knothole Village to celebrate their victory. Sally and Antoine hang a picture of the toppling machine on a wall. Sonic claims that it was his "magnetic personality" that inspired Sally to use a magnet to defeat Robotnik and his Badniks.