On her way home from school Alex Mack is practically hit by a truck. The truck is carrying a top-secret chemical and spills it on Alex. Alex learns later that she has magical powers and shares this secret with her sister, Annie, and best friend, Raymond.

Alex and Raymond are continually harassed by upperclassmen Jessica and Ellen. One afternoon Jessica trips Alex in the school cafeteria as Alex carries a tray full of food. A food fight ensues and Vice Principal Heller assigns Alex, Raymond, Jessica and Ellen to clean up the cafeteria every afternoon. Both sets of friends blame each other for the trouble, and they agree to take up Raymond's challenge of two-on-two on the basketball court. The stakes: the losers have to admit responsibility to Heller and clean up the cafeteria by themselves.

Alex asks her sister for help with a class science project, but ends up using her power to impress the teacher. This gets her into trouble when the teacher believes that the project was done by Annie, not Alex. Meanwhile, Dave and Vince disguise themselves as janitors in an attempt to find Alex.

At career day at the plant, Alex is taped using her powers and she, Ray and Annie have to sneak back and get the tape.

Annie's science project has been chosen as a finalist for the big science fair to be held at the Paradise Valley Chemical Plant. The whole Mack family is looking forward to spending Saturday at the science fair rooting Annie on, except Alex. Not only is she sick of witnessing Annie's triumphs, but the chemical plant is the worst place for her to be. It's crawling with plant spies who are constantly on the look out for "the kid."

In anger, Alex jeopardizes her mom's job. Later, she tries to make it up to her.

The plant closes in when Alex's journal, detailing her powers, ends up in the wrong hands.

Alex steals a test to help Nicole, who is cracking under the pressure of the exam. At the plant, George discovers that GC-161 has the capability to alter human genetic structure.

After a collision with a pole during a baseball game, Ray gets superpowers and goes public. He even negotiates an endorsement deal with the plant. When Ray finds himself trapped and submitted to test after test, he uses his powers to escape from the plant.

Alex makes the track team, but will she compete in the big meet once she realizes the plant is spying on her?

Alex and George discover that gifts and decorations aren't as important as the Christmas spirit, while Dave's gift to Vince is a chimp that runs amok in the plant.

While trying to impress Bryce, Annie goes mountain climbing and is left dangling.

Ray captures Alex's powers on video and wants to enter the tape in the Atron JH Video Award contest--but Danielle and Vince are the judges!

George and Barbara run into Danielle when they go to a resort to relax. When Kelly finds out that Alex's parents are out of town, she befriends her and arranges a party that destroys the house. Alex uses her powers to get rid of the guests and clean up. When Kelly heads for the door, Alex confronts her for taking advantage of her trust.

Alex is upset when Annie agrees to go to the plant carnival with Bryce instead of her. Meanwhile, Danielle must contend with a former employee who has returned to the plant--as a government inspector.

Alex, Ray and Louis rescue a kid trapped under a cement pipe in the park. When Louis accepts all the credit and becomes the town's local hero, he falls under the plant's suspicion of having the special powers.

Alex carelessly uses her powers and ruins Annie's interview with MIT. She runs away, thinking everyone would be better off without her.

Alex and Robyn get jobs at the new video store in Paradise Valley, where Vince and Dave have installed the plant's latest GC-161 detector.

Alex has to use her powers to escape from a trap set by the plant after Vince spreads the rumor that they have the GC-161 kid in custody.

Just when Alex is feeling ordinary, she befriends Paradise Valley's new wild child who favors blue hair, tattoos and nose rings. Alex goes wild herself until she realizes the value of her true identity. Vince, fired from the plant, looks for the GC-161 kid himself.

Inspired by "Cyrano," the school play, Louis helps Ray court the girl of his dreams. When she falls for it, Ray has to face two mistakes: his girlfriend is superficial and his superficial charms are about to run out. Alex's attempted rescue makes things worse. Meanwhile, Annie gets an internship at the plant and gets some romantic ideas of her own.

Alex is overwhelmed when an attractive guy starts looking her way. When he requests her as his study partner for "Romeo and Juliet," she can't control her chemical glows. It takes many blushes before she realizes that there is less to him than meets the eye. Things get worse when Dave spies on the kids and assumes that Alex's "Romeo" is the GC-161 kid.

Annie becomes obsessed by her work at the plant. An experiment she is conducting with her good-looking lab partner drives Alex out of their room and into the wood shed. Annie's partner betrays her, and she realizes that she's been a selfish sister to Alex.

Math is the ultimate challenge for Alex, and when she starts cheating, she can't stop. For help, she turns to Annie, who steers her back to her senses. However, Dave has been spying on Alex and has begun to question some floating exam books and other mysterious phenomena.

Alex befriends an unpopular guy and finds that her own friends turn on her. She blames them until she realizes the unpopular guy has a thing for her. Ray has an unlikely adventure when Dave helps him pass a driving test.

In a surprising move, Alex tries out for cheerleading...and makes the team! But while she enjoys her new popularity, she misses her carefree life. Louis accidentally switches diskettes with Annie so that she narrowly escapes getting in trouble with the evil Danielle Atron.

Alex gets a job with Louis at his dad's distributing company so she can buy her own car.

When Robyn joins an environmental group the donut shop is threatened and Alex's friendship with Gloria is tested.

Alex tries to rescue a chimp named Oscar from Vince by secretly keeping him as a pet. Annie is forced to tell George the truth about GC-161.

Alex saves a woman's life but can't tell the authorities that she double-morphed the woman to the hospital. The mystery heightens Danielle Atron's suspicions. As Annie prepares for college, a bittersweet realization comes over the sisters who share so much.

Alex struggles in Spanish class with a tough teacher, then struggles with the possibility that she got the teacher fired. Lars sets Dave up to be the first human research specimen for dangerous GC-161.

Ray is purposely mysterious about his new girlfriend, Rachel, so that Alex won't get jealous. Alex becomes jealous anyway and struggles with accepting a new friend.

Alex becomes friends with the new boy in school, Hunter, who may know something about the GC-161 project.

When Hunter finds out about the GC-161 accident he starts searching for the GC-161 kid in order to expose the plant and uncover the truth about his father's disappearance.

After four years of keeping her powers hidden, Alex's secret world is falling apart. As the Plant prepares for the release of GC-161 to the public, her dad loses his job, and Louis discovers her secret powers, and is captured by the Plant.

The final episode. Ray, Louis, and Hunter try to free Alex and her parents from the Plant which is lined with bombs thanks to Danielle Atron. Meanwhile Dave works with Gino and the FDA to stop the chemical plant from releasing GC-161.