The episode starts out in outer space with a bluish-colored alien ship being pursued by a larger reddish ship. The smaller ship takes fire from the larger one, but it manages to withstand its power and able to return fire. Within the large red ship, a profile of an alien commander known as Vilgax is shown, and orders his crew to disable the vessel to retrieve what he calls, the Omnitrix. Content in his knowledge that he is undefeatable, he ponders on who can possibly stop him. Then the scene switches to a school and shows a profile of a 10-year-old boy.
In Ben Tennyson takes a quick glimpse up to the oom's clock, and is impatiently waiting in his seat for to end. While he waits, he makes a paper airplane, aims, and throws it at his teacher, hitting the backside of her head. The bell then rings and everyone flies out. Before he reaches the doorway, Ben is stopped and has to listen to a quick word from his teacher concerning the airplane he threw.
Outside, two bullies are picking on a smaller kid for his money. Seeing as how summer vacation has started, they decide to be lenient with the boy and just take the money without beating him up. Ben attempts to help him, but only succeeds in getting both himself and the kid beaten and hung from a nearby tree by their underwear. Despite Ben's obvious predicament, Grandpa Max tells him to hurry. Ben points out his situation to him and asks to help him get down.
Ben is excited about the trip, but it was quickly drawn away when he finds his 10-year-old cousin, Gwen Tennyson, is already in the RV. She is no more excited about the situation than Ben is, having already a well-planned specific schedule, but only to find that Grandpa Max convinced her mother to go along with him on the trip. Both look unhappy and pout. Max points out that it will be a long vacation.
At their campsite, Grandpa Max decides to make dinner. His idea of dinner differs from Ben and Gwen's taste, in that it is live, marinated mealworms. When the two ask for some "real food," Max acts as if the mealworms are just as tasty as any other types of food. Max enters back into the trailer, and Ben and Gwen go over the food they brought with them, wondering how many days they can stretch some candy and chips over. They then continue to look down how bad this trip will be.
Back in space, the two vessels continue their fight with each other, though Vilgax successfully disables the propulsion systems of the smaller ship. They prepare to board, though the smaller ship had enough energy just to make one last-ditch shot directly hitting the ship's bridge, seemingly with Vilgax along with it. His ship then returns fire with a far more powerful blast, and it nearly vaporized the smaller one. It floats dead in space, though a small escape pod is released and heads towards Earth. It breaks apart on the way, revealing a small, sphere within it.
Back at the campsite, Max tries to encourage Ben and Gwen into doing some camp-related activities. His efforts fall on deaf ears, though, since neither one is willing to participate. Ben, however, gets up to take a walk in the woods. As he does, he complains about his luck in regards to his vacation. As he looks up, he sees at what he believes is a shooting star. It changes course and nearly crashes onto him. Ben examines the crater and finds a sphere. It then opens up to reveal a strange looking device, appearing to be a watch. With extreme curiosity, he moves his hand closer to try and take it, but the watch clamps itself onto his wrist. He tries to shake it off with little success, and immediately goes back to his Grandpa what just happened.
As he heads back to the campsite, he decides to fiddle around with the device first in attempt to remove it. In response to his fiddling, the face of the watch pops up, and reveals a silhouette of some kind of creature. He immediately presses the face of the watch not thinking of what it may do. It promptly transforms him to an alien named Heatblast, a fiery alien capable of creating fire at his own will.
He is freaked out by what just happened at first, believing himself to be on fire. Ben quickly realizes what has happened and starts toying with his new-found power. This backfires on him when he starts a forest fire. Back at the campsite, Gwen and Grandpa Max notice the fire. Grandpa Max immediately assumes it to be some foolish camper toying with something he knows nothing about; however, he quickly connect that statement to Ben. They head over to the fire and try to put it out.
At the source of the fire, Gwen is the first to find Ben, and attacks him in fear. Unable to get her to listen, Ben has some fun by lighting one of her shoes on fire. This only makes her angrier, but she realizes that the creature is Ben after hearing him talk. She queries him on his strange appearance, and Ben tries to explain. Grandpa Max shows up shortly after, and Gwen brings him up to speed. Ben almost goes into his explanation again, but Gwen stops him. Aware of the rapidly growing fire, Grandpa Max has Ben start a back-draft to put it out. A ranger arrives later, clearly confused by the large section of the charred forest.
Back in space, it is shown that Vilgax has survived the destruction of the bridge, though his current condition suggests that he might have been better off not surviving. Three of his limbs are practically gone, with only a small portion of his right arm intact. He is forced to stay inside a regeneration tank while tiny robots heal him. A subordinate officer informs him that the Omnitrix was sent to the planet nearby them. This definitively reveals the nature of the device on Ben's wrist. Vilgax orders a nearby robot droid to retrieve it.
At the campsite, the three are roasting marshmallows. Ben's current condition is helping immensely in that regard. As they discuss his predicament, Gwen wonders if he'll be stuck as a monster forever. Grandpa Max quickly corrects her by saying that he's an alien. After a confused stare from the other two, Max tries to cover up his odd knowledge by saying that Ben couldn't possibly be anything else. Ben then echoes Gwen's earlier sentiment about being a monster forever. As Max reassures him that they'll figure it out, the symbol on his chest blinks and makes a noise, and he reverts back into his regular self. Ben is happy about the change, but still annoyed that the watch will not come off. Max orders him not to mess with it and heads for the crash site.
At Vilgax's ship, the robot that was sent to retrieve the Omnitrix finally departs and heads for Earth. Upon landing, it grows into a far larger robot with three legs. It lands near the crash site and immediately finds the sphere that held the Omnitrix. It vaporizes the sphere with one of the blasters on its hands. It then releases two drones to gather information.
Ben is trying to figure out how the Omnitrix works. Gwen warns against him doing so, but Ben ignores her point. She acts indifferent to the device, apparently unconcerned with the mysteries it holds, or what it can do to him. Ben finds her attitude confusing, wondering if she really is related to him. Meanwhile, Grandpa Max finds the remnants of the sphere. Its current state does nothing to ease his mind.
Back at the RV, Ben is still trying to figure out the Omnitrix. He thinks that if he can use it properly, he might be able to help without making things worse. He finally figures it out and prepares to activate it again, this time highlighting a silhouette of a canine-like alien. Gwen is still warning him not to use it, but he does so anyway. This time, he transforms into Wildmutt, an alien with an appearance of a large canine, and has enhanced senses. Gwen examines the new form, quickly discovering that it has no eyes. She tries to take advantage of the situation by hitting him with a stick, but the enhanced hearing of the form allows Ben to dodge easily. He then bounds off into the forest to test out his newfound form further.
As Ben roams about the forest, one of the drones spots and attacks him. It is no match for Ben, of course, and he takes it down easily. Unfortunately, he reverted back to his regular self after doing so, just in time for the second drone to find him. Luckily, Gwen arrives to beat Ben's would-be attacker into submission with a shovel. Ben is glad for the help. The two flee when the drone catches fire. It explodes shortly after.
At the RV, Grandpa Max chides Ben for his "joyride" with the Omnitrix. Ben apologizes for using it, but tries to put a bright side on the situation by showing that he can use it properly. He has also figured out the number of forms he is limited to, which are ten different aliens. He still hasn't figured out how to prevent it from reverting him back to a human, though. Grandpa Max seems eager to help him learn more about the device. Ben is overjoyed about this. A call for help on the radio interrupts them. A ranger is claiming to be under attack by a giant robot. Ben assumes it to be the source of the drones. He also figures that it must be after the watch. Knowing the attack to indirectly be his fault, Ben is eager to help.
The three head over to the site of the attack to stop the robot. As they reach it, Ben activates the Omnitrix and settles on a silhouette of a hulking alien form. Once activated, it transforms him into Diamond Head, a crystalline alien. They move on to find the robot blasting vehicles left and right in an attempt to find the Omnitrix. As Ben instructs Gwen and Grandpa Max to help and evacuate the campers, the robot grabs the ranger. Ben gets its attention before it can do anything to the ranger. Upon noticing the Omnitrix, it tosses the ranger aside and heads for Ben. At first, the robot proves to be a far better fight than Ben, pretty much tossing him around like a rag doll. During the battle, an errant laser blast forces Ben to save Gwen from being crushed by a tree. Ben gets an idea of what this alien form is capable of, and the battle begins to turn. Ben eventually wins by reflecting and redirecting the robot's own lasers back at it, slicing it in half. After some cheering, Gwen and Grandpa Max motion to Ben to make a quick exit, leaving the other campers pondering who has just saved them.
Back at Vilgax's ship, Vilgax is understandably upset about the defeat. He promises to make a trophy out of who is keeping the Omnitrix from him. Until then, he is confined in his tank, and plots carefully of what he may do next.
As they were getting ready to leave, Ben seems to have gone missing. As Grandpa Max wonders where he could have gone, Ben arrives in yet another alien form. This one is referred to as XLR8 (pronounced "accelerate"), a super-fast, lizard-like alien. Ben uses its abilities to quick pack everything into the camper. He then remarks that this summer will be the best one ever. Grandpa Max agrees, and Gwen merely says that it will be somewhat interesting. When questioned about his absence, he merely claims that he had something to take care of. A quick retreat to another part of the city shows the bullies from before hanging by their underwear on the tree. Their short conversation makes it clear that Ben was responsible for their unfortunate situation.