Ben goes on a road trip with his Grandfather, and cousin Gwen for summer vacation. When they stop at a forest, a meteor crashes nearby. Ben approaches the remains, and a device attach's itself to his wrist. Now he can change into 10 different alien creatures. Ben must learn to use the watch and each alien with forces intent on taking the watch.
Making a stop in Washington D.C., Max uses the watch to stop crime and rescue people, but he wants some reward. Grandpa Max tries to teach him what a hero really is, but his first encounter with Dr. Animo, a scientist who can mutate and control animals, will really teach him.
The group goes to visit Aunt Vera whose now living in retirement community. Ben witnesses some of the residents climbing walls, and other superhuman behavior. When Grandpa Max, is affected it's up to Ben and Gwen to find out what's going on.
The Tennysons go to a circus, but something's bothering Ben. Ben leaves the circus as the Circus's Star performer, Zombozzo the Clown stars his act. Ben foils a crime, and returns to find the circus has disappeared, Grandpa Max is acting strange, and Gwen has vanished. Ben must overcome his personal fear to rescue his cousin.
Ben foils Hex's attempt to steal a spell book, the museum gives him some souvenirs. Gwen gets jealous of the attention Ben receives. Ben gives her a souvenir. Soon she finds out it's a magic charm, and everything's going her way. Now the Tennysons have two superheros in the family.
Ben is too short for a ride at a water park, so he uses the Omnitrix to sneak in. An alien enthusiast captures Greymatter and wants to announce it to the world, so he contacts the Organization, who wants the alien for their own plans.
Ben wakes from a nightmare and says an alien is coming after him. Grandpa Max tells them they're going to Mt Rushmore immediately. The alien from Ben's dream attacks them along the way. Ben tries to fight him, but the alien seems to know the Omnitrix's abilities. Grandpa doesn't stop to help Ben, he and Gwen continue to their destination, he reveals some secrets to his past, and his connection to the alien. Grandpa hopes to gather some weapons to help Ben in his battle.