Chuck Versus the Nacho Sampler

While training Hannah on Nerd Herd procedures, Chuck is called away by Casey to attend a briefing in Castle. Beckman announces to the team that the Ring has transferred a sizable amount of money to a computer engineer named Manoosh (Fahim Anwar) and orders Chuck to gain his confidence to determine the nature of his work with the Ring. She has made arrangements that will force Manoosh to come to the Burbank Buy More, where Chuck is to make contact. Sarah has misgivings over whether Chuck is ready, but Casey is confident. Chuck, however, overplays his effort and botches the contact. The team makes a second attempt later that night at a local Mexican restaurant, where Chuck arranges an "accidental" meeting at the bar. After being coached through how to ingratiate himself with the asset by Sarah and Casey, Chuck manages to get Manoosh to divulge that he is working on a weapon. During the conversation, Manoosh is contacted on a Ring Communicator by his Ring handlers, who are closing in. Sarah takes over to accelerate things and tranquilizes him.

Back at Castle, Chuck, Sarah and Casey examine Manoosh's briefcase, and find a suspicious object within. While Casey examines it, Chuck returns the briefcase to Manoosh—who was earlier carefully released by the team to hide his actual whereabouts and is now waiting at the Buy More—so he can be on his way. Chuck is recalled to Castle in time to see Casey successfully break into the device, only to discover it is a decoy. Meanwhile, several Ring agents corner Manoosh near the Buy More's loading dock. Chuck and the team watch in surprise as he takes out a pair of sunglasses and flashes on advanced kung-fu. He quickly defeats his assailants and flees. Casey, Sarah, and Chuck conclude that the Ring contracted Manoosh to rebuild the Intersect from burned out components that they stole from a CIA facility.

Manoosh is tracked to Weap-Con, the world's largest weapons convention, in Dubai and the team follows him. They watch from the audience as Manoosh demonstrates his Intersect device for several dignitaries and high-ranking military officers, then corner him backstage before an auction can be held for the technology. Chuck warns him not to proceed, and reveals his identity as a spy. However, before Manoosh can flee or the team can take action, several Ring agents intervene and capture the four. Chuck, Sarah and Casey are imprisoned, and Manoosh is threatened to turn over the device, but destroys his prototype thinking they will have to keep him alive. Before he can be killed, the team breaks out and confront Manoosh and the Ring agents, who are defeated. Chuck initially allows Manoosh to leave, but as his asset is walking out, tranquilizes him instead when he sees Casey about to do so for him. To protect him, Chuck turns Manoosh over to the custody of the government once they are back in Burbank. Casey acknowledges Chuck is becoming a spy but Sarah wonders aloud whether it's truly a good thing, while back at home Chuck turns to alcohol after being forced to "burn" his asset. Sarah has a flashback to the first day she met Chuck, she thought he would be a "piece of cake".

Chuck is attempting to train Hannah for her new job with the Nerd Herd. Jeff and Lester immediately take a liking to her and begin making advances, until Chuck and later Morgan, who has his own interest in Hannah, warn them to back off. Morgan later convinces Jeff and Lester into stalking her to learn as much about her as they can so he can make himself look better to her. Morgan is crushed when Hannah mentions Chuck's trip to Paris, as she believes it was an install and is unaware that no one else knows about it.

Meanwhile, Devon is still recovering from his experience as a prisoner of the Ring. He is jumpy and hasn't been interested in exercising, and his relationship with Ellie is suffering due to his difficulties in lying to her, especially when Ellie finds a luggage claim ticket from Chuck's mission in Paris. Devon confronts Chuck about the situation, but hides when Ellie arrives as well to complain that Chuck didn't tell her about his trip. Devon is shocked and outraged at the ease with which Chuck lies to her about his trip being an install for a Buy More customer. Chuck also tells Ellie that he is sending her and Devon to Paris for a proper honeymoon, but Devon doesn't accept Chuck's explanation that he has to lie to keep them from witness protection. When Chuck later has tickets to Paris delivered to Ellie, Devon gets angry and demands Ellie refuse them as they "come with strings attached" before storming out again. Ellie runs into Morgan on the way out, and both lament about Chuck and Devon's strange behavior. Morgan promises to find out what's going on, and taps Jeff and Lester to spy on Chuck.

• Manoosh flashes twice on advanced kung-fu using his glasses: Once to defend himself from Ring agents in the Buy More parking lot, and the second during a demonstration of the device.
• Chuck uses a knife-pen as a throwing knife after flashing on a shuriken display during the fight at Weap-Con.
• After another flash during the fight, Chuck uses a plate of nachos provided for Manoosh as a discus to save Sarah from a Ring agent.