A man and his assistant are trying to experiment time-travel by using quartz crystals, but the experiment fails, causing the man to be sucked up into the portal, while the shadow of an unseen creature is seen and heard growling.
Ben, Gwen and Kevin visit Los Soledad after hearing of a disturbance. The place is wrecked and they see materials partially sucked up in an old machine and fossilized animal skeletons. There are also trails seemingly burned into the ground and through walls. Suddenly, a creature arrives and Ben changes into Chromastone to fight it.
The creature gets away and Chromastone changes back. Then they sees a mysterious man and Ben changes into Swampfire. The man disappears and then reappears offering Swampfire a gumball. The creature reappears and Kevin tries to fight it, but strangely, punching it changes him into an old man.
Kevin begins acting like an old man and Ben tries driving Kevin's Car to escape the creature. The creature soon chases them and ages Kevin's car to a rusted broken car. They eventually escape the creature and meet the man again, who changes Kevin back to his proper age. However, he says regressing a car is beyond his ability. Ben asks the man who he is, and the man explains back in the 50's, he was involved in an experiment involving time-travel.
The man was sucked into the portal and was trapped in the space-time continuum for 100,000 years or more, having not to age, sleep or eat, just exist. He became insane but got bored and decided to learn. He now has a total understand of the space-time continuum, enabling him to travel any where and when he wants. Gwen decides to name the man Paradox as he forgot his real name.
Paradox's current concern is the creature they've encountered. The creature came into their plane of reality when his experiment went awry. Gwen points out that this creatures couldn't have been around for fifty years, as they would've known about it. Paradox explains that his experiment flung this creature to the present. Ben and team ask why the creature needs to be stopped if it's only attacking an abandoned military base.
Paradox then brings them to the Moon (for some reason, with a breathable atmosphere) and shows the team the best possible future if the creature wasn't stopped, Earth turned dark and brown. They then spot a future Paradox who had failed to prevent this catastrophe. The future Paradox urges his counterpart not to repeat his mistakes and sends them back to the present. Gwen suggests that they simply go back and prevent the time experiment from happening. Paradox says they can't do that because it would also prevent him from becoming a time traveler who has helped the universe hundreds of times. He almost mentions one adventure that he and Ben had in saving the universe. They then spot the creature. Ben transforms into Jetray and shoots the creature, but the creature was immune to the beams. Paradox throws some gumballs to the creature and momentarily slows it down due to the fact gumballs can last a long time.
Ben, Gwen and Kevin see that the creature wasn't acting like an ordinary creature, but a man looking for help. They try to fight the creature and decide to stop it from being created by traveling back to the accident. Paradox then grapples with the creature. Though he exists outside of time, he says he can still feel the eons passing. It was revealed that the creature was Paradox's old assistant Hugo and he was transformed into an inter dimensional creature traveling forward 50 years.
Ben saves Hugo by turning into Humungousaur (who turns out to be the unseen creature from the beginning of the episode), and keeping him from getting sucked into the portal. The Hugo that was with them changes back to normal and they go back to the present, where they meet an older Hugo. Paradox offers Hugo a chance to time travel and they leave Ben and his friends to explore time.
As Ben and friends were about to leave, Kevin cursed Paradox for not changing his car back. But once they go to the exit, they see Kevin's car, brand-new, with a note left by Paradox saying: 'Kevin, try to keep in mind that if this car comes into contact with anything else from 1976, it will explode like anti-matter. Enjoy! -Paradox.' Ben, Kevin and Gwen then drive back home, with Kevin querying if that note was a joke.