Synopsis
In a flashback, Samantha Eve Wilkins / Atom Eve battles against the villain Killcannon and defeats him. She is then asked by fellow superhero Robot to join his group, the Teen Team. Eve returns home and is forced to reveal her superhero identity to her parents. One year later, during a patrol, Eve spots a green female alien flying in the air, though she is forced to deal with Killcannon once more. Eve quickly dispatches of him, before letting the Teen Team take care of the situation. The next day, Eve begins her senior year at high school. The Teen Team responds to a robbery committed by the Mauler Twins, where they are assisted by a mysterious pajama-wearing superhero who calls himself Invincible. The next day, at school, Eve encounters fellow student Mark Grayson, who reveals himself to her as Invincible. The two of them befriend one another, as well as Mark's friends William Clockwell and Amber Bennett.
Later, Eve encounters one of the students at her school, Todd, who has a chemical bomb crudely grafted to his chest. Eve can either defuse the bomb in time or prioritize saving nearby citizens, resulting in Todd's death. Regardless of the outcome, Eve proceeds to investigate the origin of the bomb. Her investigation is cut short by reports of disturbance at the city's power plant. Eve arrives and finds the green alien she encountered earlier, who is siphoning energy from the plant's reactor. The alien, calling herself Universa the Warrior Queen, battles Eve, while claiming that her world is dying and that she needs the energy from Earth to save it. Eve defeats Universa and destroys her staff, knocking her unconscious. Robot arrives and apprehends Universa, though he does not allow Eve to pry further on Universa's story. As Eve's investigation on the bomb goes further, she soon discovers that her chemistry teacher, Hiles, was the one who created the bomb, and she was working together with the Mauler Twins. Teaming up with Mark, Eve defeats the Twins, then later makes a choice whether to let Hiles commit suicide with her own bomb, or stop her from doing so. Regardless of the outcome, Robot confiscates Hiles' bomb design blueprints, though he is forced by Eve to promise a chance to speak to Universa later.
On graduation day, Eve, Mark, William and Amber celebrate going to college, though Eve admits that she did not send in any applications, as the choice did not appeal to her. Their celebration is cut short by news of the deaths of the Guardians of the Globe, the world's leading superhero team. Eve and Mark attend the Guardians' funeral, but Eve becomes frustrated when her boyfriend, fellow Teen Team member Rex Sloan / Rex Splode, fails to attend. She later finds out that Rex has been cheating on her with another team member, Kate Cha / Dupli-Kate, due to growing jealousy of Eve's friendship with Mark. Heartbroken, Eve breaks up with Rex.
Some time later, Robot informs Eve that he has been selected by the Global Defense Agency to lead a new chapter of the Guardians, which also means the disbanding of the Teen Team. Eve declines Robot's offer to join the new Guardians. Returning home, Eve argues with her parents about her breakup with Rex, then furiously leaves them as she goes to the suburbs, where she creates a treehouse to take refuge. The next day, Eve is contacted by Cecil Stedman, director of the GDA, who reveals that Universa wishes to speak with her. However, their conversation is interrupted, as Eve then learns Mark is embroiled in a battle against his father, Nolan / Omni-Man. Eve attempts to go help Mark, but is stopped by the villain Doc Seismic. Eve deals with Seismic, but then finds that Omni-Man has retreated into space, while Mark has been hospitalized.
Some time after the incident, Eve reunites with William and Amber, the latter of whom has broken up with Mark due to him constantly canceling their dates. As Amber begins to figure out Mark and Invincible are the same person, Eve contemplates disclosing her superhero persona to both Amber and William. Eve goes to a GDA prison facility and meets with Cecil, who lets her into Universa's cell. Universa pleads with Eve to recover her Staff of Leadership, so that she may leave the planet and search for other resources for her people. Eve finds one half of the staff in Killcannon's possession, and the other at the power plant. Eve recovers both pieces and mends them back together.
After visiting a recovering Mark at his home, Eve takes Universa's staff back to the GDA prison, but Universa escapes her cell and takes the staff with her. Eve begins preparation to face off against Universa one final time, while also accepting Robot's offer for assistance. Eve returns to the power plant, where she battles both Killcannon and Universa. Ultimately, Eve can make a choice whether to trust Universa and help her siphon energy from the power plant's reactor, or help the GDA apprehend her. In the aftermath of the battle, Eve returns to her treehouse, hopeful for the future.
