When JESSIE PALERMO is shot at school, Palermo pulls out all the stops to find out who's dealing the guns to the students. He consults with local gun manufacturer CAVANAUGH, who is mystified that guns without serial numbers could leave his factory. T.C. goes undercover as a substitute teacher at the high school while Chris and Victor go undercover for a sting operation. The squad traces the guns back to the supplier -- KYLE CAVANAUGH, the factory owner's son... and the boyfriend of Jessie's best friend ERICA.After the shooting, Jessie returns to school but continues to suffer emotional turmoil. Her best friend, Erica, doesn't understand and becomes more involved with her boyfriend. Jessie does some investigating into the shooting on her own, but doesn't expect her assailant to be school geek JOSH TIMMONS, who had purchased the gun to ward off bullies.