Megan Walsh or Agent 83 is an orphan in the government-run Prescott Academy. She trained to become assassins. She has a top skills, which have made rivals with Agent 84. She starts life as a normal teenager, adopted the name Megan Walsh and going through an exchange program to live with the Larson family. Mrs. Larson is kind, son Parker instantly likes Megan, but daughter Liz is cold and distant. Megan attended to the class with Liz. Megan soon make friends with Roger, a geek and has an interest to her. Megan is attracted to Cash, hacking the school's system to make him her biology lab partner, to the ire of two mean girls.
At the homecoming dance, Megan realizes that Cash is a boring person and dumps him. She goes to apologize to Roger, but finds out that his date is Heather, who provokes a fight with Megan. Their fight rambles through the hallways and into the school's kitchen. Heather reveals she joined Knox's operation in order to get a chance to kill Megan. Liz sneaks up on Heather and stabs her in the leg with a skewer from a corndog. Meghan then uses a frying pan and hits Heather in the head knocking her unconscious and she falls to the floor. The girls return home to find that Knox and some models have taken Parker and Mrs. Larson. Megan fights the goons but Liz gets captured as well. Knox reveals that she was Prescott Agent 1, but she left and turned against them. Hardman shows up with reinforcements and defeats Knox and her goons. Megan uses a Prescott helicopter to stop Roger, who is driving home with his father. She tells Roger her true feelings for him and they kiss.