Archie Sonic the Hedgehog Issue 31 was the thirty-first issue of the main Sonic the Hedgehog comic series.
- "A Robot Rides the Rails"
While on an information gathering mission in Robotropolis, Sally discovers that a train carrying the Dynamac-3000, Robotnik's latest super robot, is leaving for the western part of the continent. Eager to stop it, Sally boards the train, and the Freedom Fighters quickly mobilize to join her upon realizing what's going on. Boarding their plane, they set off to join Sally, who finds the offline Dynamac only to be grabbed from behind by a mysterious figure. Sonic attempts to catch up to the train, only to be knocked down by its defenses.
Sally's assailant is revealed to be Geoffrey St. John, who greets Sally with a kiss after letting her go. Receiving a rather cold response, he reveals that the Rebel Underground has also been making plans against the Dynamac-3000. Meanwhile, Sonic recovers from his run in with the train and is picked up by the other Freedom Fighters. At the same time, Geoffrey's men cut the power in the engine compartment, only for the Dynamac-3000's fail safe systems to bring it online. Tails drops Sonic onto the plane, only for Dynamac to burst through the roof.
Swat aside by Dynamac, Sonic runs into Sally and Geoffrey, and instantly dislikes Geoffrey for mistaking him for another trainee like the Substitute Freedom Fighters. As the Dynamac changes form to attack the Freedom Fighter plane, the heroes use NICOLE's information on the Dynamac to determine a weak spot. Sally is then grabbed, and both Sonic and Geoffrey's attempts to free her are met with defeat. Deciding that they need to work together, the two rescue Sally while the Freedom Fighters draw the Dynamac-3000's attention. Sonic then inserts a device that shorts out the robot's systems, allowing Rebel Underground agents Dolph and Jean-Claude to take it out.
Parting ways, the Freedom Fighters board their plane while the Rebel Underground claims Robotnik's train. Sally and Geoffrey kiss each other goodbye, prompting a bit of a negative response from the other Freedom Fighters.
- "Lost... and Found!" - Part One
Knuckles continues his search for the missing Chaotix members, to find the ancient ruins and the mysterious Archimedes. He is being watched via surveillance network where the shadowy Archimedes watching Knuckles. He continues walking through the deserted area and notices a sign from Archimedes reading "Grand Conserve." Knuckles walks off into the night to try and find his teammates.
- "Tundra Road" - Part One
Woken from his sleep by the sound of an old radio going off, Rotor is visited by Sonic and Sally. At first dismissing the noise because of the device's antiquated and sentimental nature, Rotor is shocked when his mother's voice once again comes through. Heading to the command center, the trio discovers that there is indeed a radio signal coming from the Frozen North Sea. With Sally's blessings and Sonic's confusion, Rotor sets out alone in his Bathysphere, piloting it through the Undersea Canal Grid to reach the Frozen North Sea.
Once there, he finds the Walrus Herd, but to his shock they are in some sort of trance. Robotnik's voice comes on over a loudspeaker, and the herd is directed into a cave by Icebots. Playing along, Rotor discovers that Robotnik has used a Neuron Bomb to short circuit the herd's minds, leaving them pliant to his commands. Revealing his plan to have them freeze all of Mobius, Robotnik is then alerted to Rotor's deception. The Walrus Freedom Fighter flees, only to be hit in the head by an Icebot club and is left sinking into the depths of the sea.
- Geoffrey St. John: "After all, he's not just any ordinary mechanoid Robotnik is sending out to our neck of the woods--He's a tiger of deadlier stripes!"
- NICOLE: "I suggest a strategic withdrawal until sufficient back-up has arrived!"
- Sally: "Somehow NICOLE--I just don't think that's a viable option!"
- NICOLE: "Facing overwhelming odds doesn't seem brilliant to me, either."
- The Rebel Underground and Knothole Freedom Fighters team up to defeat the Dynamac-3000.
- The Walrus Herd is revealed to be under the control of Dr. Robotnik.
- In small print on the cover the train says Robotnik express this was also the name of an episode in The Adventures of Sonic the Hedgehog cartoon.
- When the Dynamac changes forms, Sonic says that the robot is "more than meets the eye". This is a reference to the Transformers series.