The SRU is called in when a gun is fired in a local bar and two local drug dealers have been beaten up. The team quickly learns that the drug dealers were terrorizing the owner of the bar (guest star Fulvio Cecere, INTELLIGENCE) and that a good citizen came to his rescue. The team identifies the good citizen as Robert Cooper (guest star Alex Carter, CSI), the president of the neighborhood guard association. When Cooper goes after and shoots one of the dealers, the team fear that Cooper is taking the law into his own hands and becoming a vigilante. The team must race to protect the dealers and save Cooper from himself.