It is dusk, and as the city sleeps, Hydrobot awakens! Leaving his owner's apartment, he soon comes across a trio of human-sized Decepticon combat drones attacking an innocent citizen. After a brief battle, the drones make a hasty retreat, but as Hydrobot moves to pursue, he is stopped by Hound, incorrectly identifying the diminutive 'bot as a Decepticon, then again by Optimus Prime, and finally by Bumblebee, before successfully escaping the clutches of all three Autobots.
With Hydrobot gone, Optimus voices his concern that if he and the Autobots fail on their mission, Megatron will be able to create an Energon convertor and wreak havoc across the world. Hound notices a patch of a mysterious substance that Hydrobot left behind, and uses his skill as a tracker to find its source - the laboratory of Doctor Hiroshi Benson at the Schick R&D department. Upon questioning from Hound, Benson reveals that the mysterious substance is called H-Boostium, and that he had synthesised it in an attempt to create the perfect razor. However, the samples he created were freed in an explosion six months ago, and bonded with a nearby prototype razor, creating Hydrobot! Immediately, the newborn Transformer used his immense strength to rescue Dr. Benson–but was gone when the doctor looked back...
No sooner has Dr. Benson finished his story than the Decepticon combat drones arrive on the scene–with backup in the forms of Barricade, Onslaught, and Megatron himself! When Onslaught moves to attack, however, he is quickly knocked over–by Hydrobot! Seeing the tiny Transformer's true nature, the Autobots rush into battle to assist him. Megatron takes Dr. Benson as a hostage, but fails to stop the human from telling Hydrobot how to use his energy-field razor's control handset to defeat the Decepticons. The control handset, in conjunction with Bumblebee's stinger weapon, creates an energy surge that instantly incapacitates the Decepticons, moving them to retreat.
With the Decepticon menace defeated for now, and the sun rising on a new day, Hydrobot makes his silent goodbyes to his new allies, and to his creator, before heading back home to live out his own life. This farewell doesn't upset Bumblebee, however, because he knows that someday, somehow, he'll be seeing Hydrobot again!