Thirteen-year-old Mark Hollander has just arrived in America from England. That night while he is playing a game, Mark discovers a new level that should not be there, level seven, during a storm lightning strikes his home and power surges into his computer -- bringing the characters to life.
Ace has been captured and imprisoned by Lord Fear, and his energy is being drained. Mark teams up with a clueless Chuck to rescue Ace. However, soon Samantha becomes part of Lord Fear's plan to destroy Mark and Ace.
Lord Fear and Pigface kidnap Mark's science teacher, Mr. Cheseborough, and replace him with Lady Illusion in disguise, as part of a trap to destroy Mark.
Mark tries to skip school but his parents encourage him to go to detention.
Ace begins to lose energy without a reliable power source to recharge. Mark's class visit Conestoga Hills' observatory, where Chuck tells the urban legend of the Radioactive Guy, a scientist who went mad after being exposed to the radioactive waves of a comet.
Lady Illusion strikes out on her own to find a way back home, stealing Lord Fear's piece of the Amulet. Mark's romance with Samantha is jeopardised when he learns Ace has captured Lady Illusion. However, to Mark's surprise, the two wayward superhumans fall in love.
Lord Fear gains another piece of the Amulet, using it summon the maniacal jester Googler and his puppets Zip and Snip. When Googler confronts Ace, his puppets zap Ace of his superpowers.
On Halloween, Mark throws a party at his house but has to rescue Chuck when Pigface and Dirt Rat mistake him for Ace, since he is wearing an Ace Lightning costume. Meanwhile, Duff turns to Ace for help to rid himself of Lord Fear.
Dirty Rat obtains Ace and Lord Fear's pieces of the Amulet in an attempt to summon his own minion, leading to the arrival of the cyborg Random Virus, Ace's old friend, who suffers from two conflicting programs.
Mark discovers Samantha has gained a part-time job at the carnival and attempts to dissuade her from taking it.
Lord Fear kidnaps Random, prompting Mark to help Ace search for him. Mark turns to Chuck for help finding a way to prevent Random from turning evil in the video game.
Mark's social life begins to collapse around him. His grades are failing, his parents ground him, and his relationships sour while Ace struggles to retrieve a new Amulet piece from the carnival.
During a battle against the villains, Ace is zombified by Googler's puppets, rendering him a brainless slave at Lord Fear's command.
Mark dreads going on a field trip to the carnival, and decides to be honest with Samantha about his feelings and his secret life.
Mark, Chuck, and Ashley have a horror night, but their night does not go according to plan.
Chuck records Sparx flying overhead on film and mistakes her for an alien, causing a frenzy around town.
Mark's friend Pete visits him, but his easygoing attitude and knack for just about everything makes Mark jealous of him.
On April Fool's Day, Lady Illusion disguises herself as Mark and sabotages his social life in school, while the real Mark is at home with a cold.
Mark tries to recruit Random Virus for help, but his evil side prevents him from being a hero.
In this clip show episode, Duff speaks to a psychiatrist about his ongoing involvement in the battle between Ace and Lord Fear.
During a fight between Ace and Lord Fear, Chuck is struck by a deflected lightning bolt, temporarily gaining superhuman strength, particularly in his foot, which he nicknames "Thunder Foot".
At the carnival, Ace finds a new piece of the Amulet. However, both he and the villains learn Mark has gone camping with his father Simon, Chuck, and Brett.
Mark has a tough decision to make between going on a date with Heather, or helping Chuck run an Ace Lightning fan club meeting at the school.
When Samantha obtains the final piece of the Amulet, both factions hope to gain it during the school play of The Phantom of the Opera.
Tired of Lord Fear's abuse, Dirty Rat is encouraged by Sparx to insight a rebellion against his master, rallying Anvil, Pigface, Googler, and Duff to his cause.
The final battle is at hand. Ace and Sparx try to recruit Random to fight but he refuses to.
Mark returns home from England, discovering Samantha is attending a boarding school, while Ace and Sparx plan to return to the Sixth Dimension with Random Virus.
Ace sends an SOS to Mark, which is picked up as Morse code, Chuck deciphering it with help from Mr. Cheseborough, realising the truth about Mark's game.
Mark invites Kat to watch movies at his house, but Heather insights an unwanted house party, getting Mark in trouble with his parents.
Kilobyte reveals himself to Lord Fear, overthrowing him and taking over the carnival. He upgrades Lady Illusion, giving her the ability to inject Ace with human emotions.
Ace encounters Kilobyte for the first time and is terrified of him.
Ace and Mark are taken captive by Kilobyte and held prisoner in the junkyard. Random's evil side joins forces with Kilobyte, but is troubled by Ace's cowardice.
Lord Fear once again kidnaps Mr. Cheseborough, convincing him that Ace is an evil alien and requires the teachers scientific knowledge to be defeated.
Mark has a bad day at school. He goes behind Chuck's back to eliminate Rotgut when he wanders into the school, destroying Mr. Cheseborough's lab.
Samantha returns to Conestoga Hills for a visit and to tell Mark some important news, but keeps getting interrupted.
Mark grows jealous of Chuck's favouritism in the Lightning Knights, allowing him to be stalked by Rotgut, who possesses Chuck's body.
Mark and Chuck investigate an encrypted database on Kilobyte, discovering his origins and confirming Ace's theory that he is a puppet for someone else.
Kilobyte begins his plans for world domination, defeating Random, and then targets Rick and Mr. Cheseborough for elimination.
Kat connects Ace Lightning to the carnival, but when she tries to interrogate Duff, she is captured alongside Sparx and Random.