Mason Whitney is tied down in Riordan Payne's lair. Riordan has given him a fatal, time-released dose of a truth-telling drug. As soon as Mason reveals where he's hidden the codes, Riordan promises to administer an antidote. Lou comes into the Buy More to get her phone fixed She owns a deli in the mall and needs the sandwich recipes in her phone, so Chuck promises to fix it by tomorrow.
Captain Awesome, Ellie are on a double date with Chuck and Sarah, Meanwhile outside Mason is roaming the streets until he collapse Ellie tends to him and tosses his wallet to Chuck. Chuck flashes on Mason's ID and freaks out, Ellie comes home to tell that Mason had died of some kind of poisoning. Sarah informs Chuck that it's time they spent the night together. Beckman informs Mason was a programmer for "Sanctuary," an updated security system for U.S. weapons sites.
The codes on his missing chip are the key to U.S. nuclear facilities. Big Mike gives Morgan a special assignment, Lou walks into the Store and brings Chuck a Sandwich to thank him for fixing his phone. Sarah walks in and introduces herself as Chuck's girlfriend. Sarah finds a strange listening device behind Mason's ear, which infused the poison into his body. Riordan dressed as a cop questions Ellie and pretends to fix her hair puts a listening device behind her ear.
Chuck stops by Wienerlicious to talk to Sarah about plans to spend their first night together. Chuck decorates his room with candles and sexy music, which doesn't make Sarah happy - they're only doing this for cover, as Casey listens in. Chuck asks Sarah about seeing other people. She doesn't think it's a good idea, and knows that he has a crush on Lou. Ellie comes into Chuck room and confesses of she did to him when they were little; Ellie passes out as Sarah finds the device behind her ear.
Government teams are racing to find an antidote for Ellie; Chuck then grabs the listening device and tells Riordan who is listening that the codes are at the hospital. Casey and Sarah have laid out plan to catch Riordan; he enter a room finds Sarah disguised as Ellie and he holds up a vial of poison and a vial of antidote as Chuck walks in, the poison falls to the floor and fumes start to spread. Riordan makes a run for it as Casey takes him down the antidote drops to the floor but Sarah manages to get it, She wants Chuck to take it, but he insists on giving it to Ellie, as they all start telling each other the truth.
Chuck finds Riordan's PDA, they proceed to his loft. Sarah takes him out by shooting his knee-cap, before taking the antidote Chuck wants to know f their relationship is every going anywhere. She says "no". The Team are being debriefed in the Home Theater Room as Harry walks in Casey tells Harry that they are spies, they end up relocating Harry to Oahu. Chuck visits Sarah and tells her that they need to end their fake relationship; Chuck hangs out with Lou at her deli as Sarah phone rings Casey asks if she said anything to compromise themselves, she says no.