Much to the Orbots delight, the Cosmic Circus is coming to town, and they can't wait to visit it. But as the Circus train approaches Earth, they suddenly change course and set off the Galactic Patrol's alarms. The train is caught by the Patrol's force fields, but the Ringleader explains that they are the Cosmic Circus and they're not invaders. Their story checks out, so Dia gives the go-ahead to let them land. Unfortunately, the Ringleader manages to eavesdrop as Dia and four other Galactic Patrol officers drop the defenses, so now he knows the procedure. Once free of the shield, the train unexpectedly plummets towards Earth, and Mighty Orbots is required to save the day.
Rondu gives the Orbots a new assignment: to find out what is happening at the Cosmic Circus. They go undercover as a team of acrobats called The Flying Robotis. Meanwhile, the Circus's connection to Shadow is revealed. Four of the Galactic Patrol officers are lured into the Hall of Mirrors, where they are replaced by Shadow-controlled duplicates. Later they managed to do the same to Dia, and now they have all five officers they need to control the Galactic Patrol's computers.
Seeing that they've been found out, the Ringleader's minions release the caged circus creatures, and the Orbots have to neutralize them. They do, leaving only the massive Elephantsaurus. They combine into Mighty Orbots and manage to subdue him as well.
Meanwhile, the Shadow duplicates have done their job, and with the defenses dropped Umbra begins to merge with the Galactic Patrol's computer. Mighty Orbots arrives just in time and puts an end to Umbra's plan, severing the connection and neutralizing the Shadow duplicates. They figure out how to release the Galactic Patrol officers and Dia from the Hall of Mirrors, and yet another Shadow scheme has failed.