A ship flies by, and a large block of ice is being taken into the vessel. Inside, aliens speculate the massive rock, and Kevin jumps down and recaps his previous battles. He's been told of Vilgax, over and over again. He places his hand onto the giant ice, and it melts to reveal Vilgax's frozen state. The aliens step back after seeing Vilgax, knowing that he is the most feared in the galaxy. Kevin says that they were both after for the same thing. The boy who wields the Omnitrix, and the one who has defeated them both in battle. Ben.
The Tennysons speculate the amazing sights of the Niagara Falls, hoping they would find another great summer day. Unfortunately, Gwen finds Ben tweaking around again with the Omnitrix. Ben claims that there might be some way to gain better control of it. As he continues to play around with it, the Omnitrix reacts and starts rotating through different alien silhouettes, making Ben think that he must have gone and busted the Omnitrix again. Ben says Upgrade, and he transforms into Upgrade. With amazement, he tries other commands, and he figures out that the Omnitrix also reacts to thoughts. He has found the master control of the Omnitrix, and he has gained the advantage to use it.
Ben, as Wildmutt, looks down into the river, and he looks back at one of the tourists, asking if they could take a picture of him and his wife. He falls overboard, and Ben changes into Ripjaws to come to the rescue. After picking him up from the water, he immediately transitions into Stinkfly to fly them back into the ship, safe and sound. Gwen and Grandpa Max are amazed by the sight they just saw.
Back at the ship where Kevin is, he looks at Vilgax, saying that he looks like any other alien he's fought. Vilgax immediately reacts and fights back, giving him a specific message telling him that he should have never said that. Vilgax throws a pillar straight at Kevin, and pushes him out the window, bringing both of them down into the old Megacruiser battle arena. Kevin says that Vilgax should be grateful for saving his life, but Vilgax gives no allegiance to no one. After finding out that Kevin knows a lot about Ben and the Omnitrix, immediately they form a partnership that will hope to get the device in their hands.
Gwen and Max relax to a nice afternoon snack, Stinkfly is up in the trees, and with Ben's personality, expect him to create more of his crazy jokes unto Gwen. He spits slime into her pudding, and laughs. Ben is happy that he is able to stay alien for as long as he likes. He throws the profit money he's gained for giving the tourists a ride. Gwen and Max both are very aware of the new feature of what the Omnitrix can do, but they both claim that it might have its consequences. Grandpa Max tells Ben to come to him for a small chat. Stinkfly transforms to XLR8, and instead of listening to what he has to say, Ben runs off with his pudding.
Vilgax analyzes Kevin's DNA makeup, and he explains that his pattern is the same as Ben's. Kevin's impatience lets him talk back. They both admit that they lost to a little boy, but Vilgax says that with his knowledge, and Kevin's connection with Ben, will give them the victory they need. Kevin immediately wants to get the situation over with, but they can only do it if the Omnitrix is active. They find the signal shortly after.
The Tennysons continue to enjoy their day, and Grandpa Max decides to take some pictures. Wildvine comes out of nowhere, and decides to dive into the water and bungee himself back up. In a series of photo shoots, Ben continues to play around with the alien forms, and in the lift, he decides to be embarrass himself in front of a few tourists. In a few moments, Vilgax and Kevin arrive, only to go after one thing. The Omnitrix.
Ben, Gwen, and Max were surprised that Vilgax and Kevin were still alive and well, especially after the major incidents that occurred upon them. Ben attempts to escape as Grey Matter, but Vilgax was able to grab him. Little did Vilgax know that Ben knew how to use the Omnitrix more to his advantage. He transforms to Diamondhead to escape Vilgax's clutches. With double the problem, and double the enemies, Ben knows that he's up for a challenge. Vilgax and Kevin both fall down the waterfall while Ben flies Gwen and Max into safety.
Vilgax and Kevin survived the long fall, and Vilgax attempts to track Ben's whereabouts. He comes down as Cannonbolt. At the RV, Max opens up yet another hidden stash in the RV, and it reveals the device they've seen before: The Null Void Projector. Max says that it's the only way to stop Vilgax and Kevin from coming back to bother them.
Kevin tries his way of luring Ben out of hiding, but Vilgax insists that they do it his way. He says that they should be able to get Ben out by using Grandpa Max and Gwen as bait. Their plan as using them worked, though Max was able to defend by using the Null Void Projector to open up the portal to the null-void. Unfortunately, Diamond Head was dragged in as well, and there is no way to get back, unless the one who holds the projector gun.
Kevin is unfamiliar of the place. Vilgax explains that the null-void is an alternate dimension of the galaxy, where the evil are banished forever. Outside, Max attempts to enter the realm himself to get Ben, but Gwen insists that he doesn't. Instead, she decides to head in herself. After all, Max is the only one who knows how to use the projector.
Inside the null-void, Heatblast is being carried by one of the aliens controlled by Vilgax. Ben uses strategy to survive the attacks ordered by Vilgax. Outside, Gwen prepares herself. She wears the Plumber suit as an honor to the family, as well as her passion towards her cousin. Inside, she encounters danger, but luckily, Gwen has things to prepare herself.
Kevin and Vilgax continue their search for Ben, while Max continues to hold up the portal. He says that Gwen needs to hurry. In an instant, Ben and Gwen find each other, and realize that they need to get out of there. Kevin was able to grab a hold of Gwen before they reached the portal that leads them out of the area, and to make it worse, they were surrounded. Ben had no other choice but to give up and save his cousin's life by giving up the Omnitrix to Vilgax and Kevin. Ben thinks that it would be a simple trade, but Kevin in an instant threw off his cousin and used a giant device that painfully tore off the Omnitrix from his wrist. The device was held in a spherical container, and Kevin grabs it for himself, saying that he should be able to use it instead of Vilgax. With a large fight amongst themselves in who would get the Omnitrix, Ben and Gwen were able to get out of the null-void. Unfortunately, the Omnitrix was left out, and Ben thought he would never get it back.
Gwen says that she has a present for Ben. At first he thought it was something that they would argue about, but it was something more valuable than that. It was the ball that held the Omnitrix. Gwen said that Ben may be dum enough to throw it awy,but she's not.In the null-void, Vilgax and Kevin were going after a decoy, which eventually exploded.
In an instant, he felt the aliens flow back into his body, and he becomes once more as the boy who was given the power to change into the alien heroes. Grandpa Max tells Ben that he owes Gwen a big-time thanks, but Ben had something else in mind. He transforms into Grey Matter and realizes that he zeroed out the master control. The episode ends with Gwen and Grandpa Max laughing.