Albedo Ben has stolen the Ultimatrix (an upgrade to the Omnitrix) from Azmuth and has used it to kidnap Gwen and Kevin.
An ill Ben is pleased to see an old friend in Tetrax but is caught off guard when Tetrax demands that Ben give him Chromastone.
Albedo Ben has stolen the Ultimatrix (an upgrade to the Omnitrix) from Azmuth and has used it to kidnap Gwen and Kevin. Ben goes to face Albedo Ben and rescue his friends when he quickly discovers that Albedo Ben has been working in conjunction with Vilgax. Ben is defeated by the pair and gives up the Omnitrix to save himself and his friends. Powerless, Ben goes aboard Vilgax's ship and faces off with Vilgax to stop his invasion of Earth in their final battle!
One day when Kevin returns home to find his house ransacked, he enlists Ben and Gwen's help to find out who did it and why. They soon cross paths with Ragnarok, a deadly criminal who recently broke free from the Null Void and is in search of a special key. Kevin is intent on stopping Ragnarok from obtaining the key, especially after he learns the truth about Ragnarok and his father.
The Plumber's Helpers are called upon by Grandpa Max to rescue him from an abandoned space station where he is being attacked by....Ben! The team must now find a way to work together as they try to save Max, stop Ben, and keep the space station from crashing into the Earth!
An ill Ben is pleased to see an old friend in Tetrax but is caught off guard when Tetrax demands that Ben give him Chromastone. Ben doesn't even have a chance to explain what happened to Chromastone when Tetrax attacks him demanding that he be handed over. Ben's situation only gets worse when Vilgax shows up and it is learned he is after the same thing. Ben now battles to save himself and discover why Chromastone is of so much importance.
Despite being warned by Professor Paradox, Gwen travels back in time to prevent the accident that turned Kevin into a monster from ever happening. Gwen returns to the present only to find that her time traveling caused a series of events that led to Hex ruling the world. It's up to her to fix the future that she created.
In the middle of fighting another Techadon robot, Ben, Kevin, and Gwen are unexpectedly transported by the Omnitrix to an alien planet named Primus. They soon discover that they are not alone and that Vilgax is there to stop the Omnitrix from its source.
Zaw-Veenull, a Luodan ambassador, asks Ben to deliver their crown prince, Tiffin, to Jarrett in order to keep peace between the two species. Shortly after they begin their trek in space, the Omnitrix malfunctions and turns Ben into an Appoplexian named Rath who wants to fight anything that breaths. Rath keeps picking fights across the galaxy with anyone who crosses their path and things don't look good as they approach the Pantophage home world on a mission of peace.
Kevin, Ben, and Gwen find a curious alien box in an alley that has the ability to turn into a robot version of whatever it sees. This spells trouble for our heroes when the Vreedle brothers show up and try to take it by force. The robot becomes very dangerous and Ben must stop the Vreedle brothers from capturing the device while also trying to keep the device from blowing up downtown Bellwood!
Ben's foe, Darkstar, convinces Kevin to join him in a quest to retrieve an ancient artifact called the Dominus Librium rumored to have the ability to help them both escape their current degenerate states. They succeed in obtaining it and use it to return themselves to their former states only to find it has stripped them both entirely of their powers. Kevin must now learn to cope without his powers and do so quickly as he finds Gwen and Ben in terrible peril.
Vilgax visits the prison that holds Ghostfreak prisoner. He gets more than he bargained for, though, when Ghostfreak begins possessing the citizens of Vilgaxia and amassing an army. Vilgax must but his pride aside and work with Ben to keep Ghostfreak from carrying out his ghastly plans.
Kevin is beginning to lose all hope that he might one day return to being normal when he is charmed by a beautiful girl that seems to understand. Kevin finds himself under her spell (literally) as Charmcaster has returned and is forcing Kevin to do her biding. Kevin has no choice but to obey his master and to destroy Ben and Gwen.
Ben is running away from a bounty hunter named Sunder who is after Ben and the Omnitrix.
A series of earthquakes awakens a Highbreed officer who had been hibernating deep under the Earth's surface. He believes that the Highbreed have lost the war and activates a failsafe device that is programmed to destroy. Ben must now work together with Kevin and Gwen, not only to save Grandpa Max, but also the world from this "giant" problem.