"A sabotaged experiment threatens to destroy all of Hero Factory. Stormer, Bulk, Furno, and Breez expect to give up their lives, but instead they wake up in another world -a world without Hero Factory. ''In this dark, mirror world, they find there are no Heroes, and any act of heroism is against the law. This terrifying new world is ruled by Von Nebula, Speeda Demon, and more villains than the Heroes can count. Worse still, this universe also has swarms of robot-controlling brains... but these have a thirst for destruction. Now, it's up to a handful of Heroes and a world of villains to stop the brains before they destroy both worlds." -summary of "Mirror World" from the book "Secret Mission #4: Robot Rampage"
The end of "Secret Mission #4" also has a excerpt from a future book, that may be from "Mirror World" It may also be just a prologue, but here it is: "The fugitive robot spent the next three hours making his way through the underground network of tunnels -doubling back on himself, leaving false trails, and doing every other trick he could think of to keep the jolters of his trail. When he was finally convinced it was safe, he emerged through a robothole onto the street..."click  for full description
He had calculated his position correctly. He was just one block from the safe house. It was important he not run now, as he didn't want to draw the wrong kind of attention to himself. He forced himself to walk as if everything was fine and he was in no hurry. Reaching to the door, he knocked four times, as he had been told to do.
"Who's there at this hour?" "A storm chaser," he answered, repeating the password he had been given. The door opened. Bright light inside the house silhouetted the figure who welcomed him. The fugitive took a step forward and then stopped. A shaft of moonlight had suddenly struck the face of the safe house's lone occupant, revealing a figure out of a nightmare. "Voltix!" said the fugitive, in shock. "Who else?" Voltix smiled and hurled a blast of electricity that knocked the fugitive flat on his back, his systems struggling to compensate for the massive charge. "There are no corrupt guards in the Citadel, runner... just foolish prisoners with too much hope and too little processing power. But don't worry, we'll smarten you up." Voltix walked up to his captive and rested an armored boot on his power core. "After all, Furno, we have plenty of time for teaching -the rest of your life." Furno -Hero, prisoner, fugitive, and now prisoner again -closed his eyes and wished he had never been created to live in such a galaxy as this."