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.
The big dance is just around the corner and Alex still hasn't been asked by the only person she cares to go with. Everybody knows she dreams of going with Scott, but he's not the one hounding her for a date. Jerry, an obnoxious, insensitive and persistent ninth-grader is relentless in his pursuit of her. He won't take no for an answer, but Alex continues to put him off.
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.""
Alex, Raymond, and Nicole are facing their first junior high school midterm in history class. Libby, the most popular girl in school, has her own ideas about surviving the midterm and studying isn't one of them. Libby decides to pull the fire alarm right before the exam.
Alex and Ray have a falling-out and Alex is afraid Ray will disclose her secret to the plant.
In anger, Alex jeopardizes her mom's job. Later, she tries to make it up to her.
A reporter from the Planet newspaper comes to the Macks' house to do a story; Alex's cold makes her powers go haywire.
Annie considers going away to school. Meanwhile, Alex's powers are going haywire and she must convince Annie not to go.
Alex uses her powers to save Ray after he freezes at a school music recital.
Alex and Dad have trouble connecting. They go on a day trip together and chaos ensues.
The plant closes in when Alex's journal, detailing her powers, ends up in the wrong hands.
Alex shows Dad the meaning of ""good golf"" when they enter the plant's father-daughter golf tournament.
Alex, Raymond, Nicole and Robyn notice a new neighbor moving in. It turns out to be Louis Driscoll, a cool-looking kid with a wisecracking attitude. The more Raymond likes him, the more Alex doesn't.
The morning before Halloween, Alex and Ray come across Paradise Valley's haunted house while delivering newspapers. The next day, Louis convinces Alex and Ray to check out the old house. When Alex takes a closer look, she's sucked in by a mysterious light and comes face-to-face with the woman of the house.
Short on cash, Alex baby-sits Kelly's little sister and is accused of stealing.
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?
Grounded, Alex sneaks out for a game of roller hockey and a night of trouble.
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.
Ray enters the brutal world of politics when he launches his campaign for eighth-grade President.
Annie aces her English Advanced Placement exam, allowing her to attend a writing class taught by a renowned author. Inspired by her sister's achievement, Alex sets her mind to engage in extracurricular activities in the hope that one will bring her some recognition. She discovers an unusual talent for cow milking and wins the Dairy Decathlon. Meanwhile, Annie experiences her first academic failure.
While trying to impress Bryce, Annie goes mountain climbing and is left dangling.
Alex thinks Scott wants to ask her to the plant dance, but Dad keeps getting in the way.
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 inspires Robyn to face the dreaded ""Rooney Runabout"" and pass P.E.
Alex is split into two manifestations of herself when George discovers a chemical that divides GC-161 into its individual elements.
The evil Alex wreaks havoc with her friends and family while Annie and Ray try to find the good Alex to recombine the two.
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.
Nicole tries in vain to petition against the plant for environmental violations. Alex is more concerned about her mysterious next-door neighbor who she sees having suspicious contact with the plant.
Alex becomes a photographer on the yearbook staff to earn extra credit. Louis develops a crush on Annie when she tutors him. Alex uses her powers to get herself paired with Scott on a photo assignment.
Alex and Ray's friendship is in trouble when he gets caught up with his basketball crowd. Meanwhile, the plant plots to get rid of George.
Alex's powers are out of control again and she finds that she has super strength. When Ray takes her for some serious heavy lifting at the construction site, they encounter two unwanted visitors: a suspicious Kelly and a news crew she has summoned to document Alex's mysterious abilities.
Alex experiences a chemical reaction to GC-161--uncontrollable bubbles. This unusual development coincides with the demise of Annie's relationship with Bryce.
In response to Alex's wish to jazz up the school paper, Louis becomes a kamikaze reporter who will stop at nothing to get a good story. This includes selling Ray out. Barbara is a student again and finds her new professor strangely familiar.
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.
Paradise Valley's radio station has a popular personality, but no one knows his true identity. Alex and Ray get bold and sneak into the station, only to discover how hard it is to live with a secret.
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.
Louis makes a great effort to impress his old friend, Spivey, including throwing a party at the donut shop which jeopardizes Alex's job. The boys have to learn that friendship involves more than first impressions.
Alex discovers that corruption is rampant in the town's ""Woman of the Year"" contest. When she tries an experiment on Louis, Alex gets yet another dose of havoc-inducing chemicals.
Alex has to decide how to handle the attention of a seventh-grade admirer. Vince sneaks into the Macks' house to spy on George's research and gets stuck in the basement.
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.
There is only one problem with Alex's new boyfriend--he's also dating Annie. In what turns out to be an innocent set of circumstances, Alex must walk away from a guy with real potential. Annie's broken heart is made worse by the fact that Barbara is following her around for a science experiment. Alex chooses to be loyal to her sister and dump the guy--at least for now.
Alex's old friends don't like her new friend, and with good reason: The plant has hired the new girl as a spy at the school, and Lars now suspects George is a mole.
While out racing bikes in the woods, Ray and Alex find a recluse who lives in a treehouse. He turns out to be one of the original GC-161 scientists. Vince and Lars learn of the existence of the scientist and Alex, Annie and Ray rescue him from the plant's goons.
A school bully picks on Alex and she must summon all her powers to resolve the ensuing conflicts. Meanwhile, at the plant, George is suspected of espionage when Annie accidentally leaks GC-161 information to Lars.
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.
Junior camp counselor is a new role for Alex, and one for which she's not well-suited. She and Kelly get lost in the woods, are chased by a bear and learn the importance of two words: friendship and rescue. George remembers his own camp experiences with mixed emotions.
Aunt Ashley is everything Barbara isn't: fancy, outrageous, irresponsible, crazy. Alex's wild go-cart ride with her aunt forces Barbara to get tough with both of them. Alex's school work suffers while her spirits soar.
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.
While Louis is innocently taking a photo, he catches Alex's zapper-gone-wild on film. He's sure he's captured some kind of UFO that will make his footage famous. Meanwhile, Alex helps George overcome his fear of bowling.
A morphing accident causes Alex to switch bodies with Barbara. Alex realizes that she's not ready for adulthood. Annie loses confidence about leaving home and talks to George about it.
When Alex and Annie are stuck at home during a rainstorm, they reminisce about the value of superpowers and sisterhood.
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.
Alex has a doctor's appointment and fears her altered body chemistry will be discovered. Robyn grieves over the loss of her hamster.
Ray, Louis and Alex form a band and have to deal with issues of leadership, fame and competition. Robyn learns the ""rules"" of dating from Kelly.
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.
Robyn moves in with Alex while her parents are away while Mr. Mack suspects that Dave may be his secret GC-161 informant.
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.
Alex plays matchmaker and sets Louis up with Hannah Mercury. Meanwhile, Ray gets a fancy new job and Alex falls in love with Hunter!
After coming to school like every day in her life, Alex notices that her parents, friends and teachers have started to act strangely. First she gets into detention with no reason and after escaping, everybody starts haunting her. But, what is really going on?
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.
