Carina (Mini Anden) is back and out for a night on the town with her friend Sarah, when Chuck and Morgan wander into the same club. Chuck wanders over to talk to Sarah and Carina, on a mission to act engaged to her latest mark, Karl (Vinnie Jones), introduces Chuck as Sarah's boyfriend. We find out that Carina is on a mission to steal a weapon from Karl, an arms dealer, and Chuck and Sarah are to go undercover to Karl and Carina's engagement party. Casey will go too, posing as Carina's uncle.
Meanwhile, when Morgan sees Carina again, he tells the Buy More gang about their past and no one believes him. Morgan convinces them he'll get Carina to come to their house warming party.
Operation Chuck heads over to Karl's house. While Carina and Casey attempt to distract everyone with toasts, Chuck and Sarah head up to the vault to steal the weapon. Chuck keeps trying to talk to Sarah about his feelings, but she forces him to keep his emotions in check to recover the weapon. After dodging lasers and recovering the weapon, he sets off the final laser at the end while attempting to talk to Sarah. Fool. Sarah is forced to rescue him and Carina makes off with the weapon. Carina drops off the weapon at the Buy More with Morgan and he'll give it to Chuck... in exchange for her showing up at the party.
Outside, Karl captures Carina and the three of them show up to Chuck and Morgan's party. Morgan, after rejecting Carina, unwittingly hands over the weapon to her. Chuck, Sarah and Karl are forced to step in and they end up in a gun standstill with Karl and goons. Chuck saves the day by setting the fountain on fire and then talking Karl down with a little love speech.
In the end, after sleeping with Morgan, Carina gives a flash chip to Sarah. She watches and it's Chuck trying to talk to her while he's trapped in the vault. Convinces he's dying, he admits he didn't run away with her because he wanted to be a spy to help others... because of what she once told him. In the end he says he loves her and it brings her to tears.