During one last stop by a toy store before Ben, Gwen, and Grandpa Max's maiden voyage across the Atlantic, Ben runs into an old bully, Kevin 11, who now has new powers. He's able to transform into aliens just like Ben, such as the "bootleg" doppelgänger of Cannonbolt — Wreckingbolt!
The episode begins with Max making adjustments to the copter, with the help of Diamondhead. Ben complains about going to Europe. Max tells Ben and Gwen that they could go to Biggie Box, while he finishes working on the copter.
Gwen comforts Ben and tells him that he should get out of his comfort zone, and leaving America is a good thing. Ben names things that he's going to miss, and points over to Biggie Box. Inside, Ben shops for Sumo Slammers, and has fun, but all of a sudden Ben hears a familiar laugh. Ben is surprised at the presence of his former bully, Kevin Levin.
Ben tells Gwen about how much Kevin used to bully him, and Ben decides to get payback. Ben transforms into Stinkfly, and flies over to Kevin. Ben shoots out goo towards Kevin, who uses a cushion to block it. Kevin notices Ben, and complements his new look, and shows him his Omnitrix. Ben is surprised about another Omnitrix.
Kevin transforms into Wreckingbolt. Kevin attacks Ben, but luckily, Ben is able to avoid him using his flight. Kevin attacks Ben again, but misses, causing a bit of damage. Ben questions how long Kevin had an Omnitrix. Kevin tells Ben that one night he had a dream, it showed him blueprints, designs. He started building it, and added a few minor modifications of his own. Ben's watch eventually times out. Kevin finds him and chases him.
Ben runs into Gwen, who tells him that he needs to find away to lure Kevin out of the store. Ben gets Kevin to follow him around. He was able to trick Kevin by hiding between some fake fruit. Ben gets to safety and his watch recharges. He notices a new alien and he transforms. He tries to find a name for the alien, until the little girl next to him says, Humungousaur. Ben agrees on the name and runs off. Ben keeps bumping into things due to his massive size, and knocks a few things over with his tail. Kevin comes rolling in and gets hit by Humungousaur's tail. Ben follows the damage that his hit caused, only to see that Kevin isn't at the end of it.
Eventually, Kevin and Ben breaks through a wall, leading them outside. They end up dangling off of the edge of a small cliff. Wreckingbolt holds on to Humungousaur's tail. Ben tries to hit him off, but Kevin's grip was too strong. Ben's watch begins to time out, and he begins to hit even harder. Gwen yells and tells Ben to let the Omnitrix time out. Ben reverts back to human, removing his tail. Kevin falls into the river floating off. After, Ben and Gwen hurries off into the Omni-Copter, ready to leave.
Later on, Kevin is seen timing out, after leaving the river. Forever Knight's drone flies in. Forever Knight looks to Kevin as a new recruit.
Ben runs into Kevin and discovers he wields the Antitrix.
Stinkfly: Hey Kev, look who's got the power now. Let's see if you think this is funny.
(Stinkfly fires some goo but Kevin blocks it with a cushion.)
Kevin: (To Stinkfly) Well, well well. How you doing old buddy? It's been a while. I like the new look. Especially the designer. (Shows Stinkfly the Antitrix) Stinkfly: Another Omnitrix?!
Stinkfly: Seriously? How long have you had that Omnitrix? Cause you seems to be out of little practice? Wreckingbolt: Okay, I admit, I haven't had it long. Few nights ago, I had this crazy dream, it was so vivid. (In a flashback, Kevin bolts out of his sleep before turned on his study lamp and drew something on a piece of paper) I had to jot down what it showed me. (takes a good look at what he drew up) They were plans, designs, blueprints! No way I wasn't gonna build it. I wasn't even sure what it was for. But it didn't take long to figure out, and with few minor modifications of my own, I got something pretty awesome.
Humungousaur: "Whoa! This is awesome! I'll call this one Gigantigecko! No, that's not good. Iguana Monster! No, that's weak. Roar Thing! Ugh. Oh, maybe Mega-Stega Dude!" Female Toddler: Humungousaur. Humungousaur: Works for me. Thanks, kid!