Chuck learns more about Sarah's past when they run into her old high school nemesis Heather Chandler. Sarah's teenage insecurities come to surface and she tries to avoid Heather at all costs. Chuck, on the other hand, does everything he can to hear more about Sarah's hidden life. When Heather's nerdy husband Mark turns out to be a key player in a new mission, the agents must attend Sarah's high school reunion to prevent the sale of potentially dangerous super-bomber plans -- all the action ends with the ultimate cat fight. Meanwhile, Big Mike leaves town for a day and Buy More's new assistant manager Lester decides to implement a new sales policy.

Chuck runs into his ex-girlfriend Jill while on a Nerd Herd call. In an attempt to save face, he lies to the girl who broke his heart and tells her that he is more successful than he really is. When Chuck flashes on Jill's boss - a research scientist who may have developed a deadly bio-weapon, he, Sarah and Casey must find out if Jill is involved. Meanwhile at the Buy More, Big Mike nearly chokes to death, which leads company efficiency expert Emmett to implement a mandatory CPR course taught by Captain Awesome.