Sarah's at the hospital, soaking in a tub of ice (apparently that's all that was needed to counteract the effects of the Norseman -- at least temporarily). She's alive, but not well, and Chuck's plan is to save her. So he and Casey head to the maximum security prison to free Alexei Volkoff, the only man who could possibly have the antidote. Unfortunately, some CIA baddie (Richard Burgi) beats them to Volkoff and takes him away before they get there. He tells them to stop what they're doing or they'll end up dead. Chuck refuses because, you know, he's the Intersect. He steals a fancy prototype motorcycle (with the help of General Redhead, which is awesome) and chases down the truck transporting Volkoff. Unfortunately, before he gets there, Burgi (also known as Decker, by the way) uses some fancy anti-Intersect shades to remove the Volkoff from Volkoff. He goes back to being Hartley Winterbottom (!) right before Chuck shows up. Which means he doesn't know anything about the past thirty years. Fortunately, though, he does know about the Norseman, which he and his friend, Stephen Bartowski had been working on. They come up with an antidote, which buys them some time but doesn't save her.
So they head to Volkoff Industries to get the real antidote from Vivian. When they arrive Hartley chickens out, leaving Chuck alone to head up to Vivian's office. She thinks he's bold and stupid, and she's not going to help him. Duh. She thinks it's all him manipulating her, about her father and everything else. Which is when Hartley shows up. Chuck and Hartley successfully convince her to take the secret identities that Chuck and Sarah were going to use to get away to leave Volkoff Industries with her father and start over. Chuck heads back to the hospital to save his bride. After a standoff outside with Richard Burgi and his army (Chuck, with the help of Volkoff Industries, brought Russian special forces with him), he gets inside and does save her. Then they get married. The vows are lovely and touching, and we flash back to their meeting and all the times they kissed and fell in love. It really could have made a perfect series finale, actually.
Until they open an envelope, Hartley and Vivian's wedding gift. It turns out it's all of Volkoff Industries' assets: $877 billion. Since the CIA's done with the Buy More and Castle, the first thing they do is buy that up. Chuck gets a final message from Decker, who tells him that he thinks he's been doing good and saving people, but he hasn't. He's just been a pawn all along, and the Intersect, the Ring, Fulcrum, Shaw and Volkoff have all been part of that. Chuck tries to get him to tell him whose pawn they are, but he won't. Casey, Chuck, Sarah, and Morgan stand around and try to figure it out, then Casey says they're fired so they can't figure it out anyway. But Sarah and Chuck offer their news about buying the Buy More and everything below it. They offer Casey and Morgan jobs working with them in the base, as freelance spies, which they accept (and, presumably, Big Mike and Jeffster! will keep their jobs upstairs). In other words, the show reset itself by going back to what it's always been. Morgan's all excited, so he picks up some sunglasses from Chuck's last effects box (left by General Redhead). They're lying on a note that specifically leaves them for Chuck. But Morgan puts them on and gets the Intersect uploaded into him. (Which is annoying, because I thought you had to have some sort of special brain to handle it, which I wouldn't think Morgan does.) He tells them "I know kung fu." The end.
A few things Chuck wants us to know: Chuck wasn't the first Intersect. Agent X was. And he became Alexei Volkoff. Whose daughter has control of a crazy weapon called the Norseman, which she tried to kill Sara with last week. Now it's "Five Days Ago." Chuck and Sarah are in bed, being adorably nervous about their upcoming wedding, which is exactly one week away. They freak out. Then they freak out some more, because: What if it's cold feet? Chuck's sure it isn't, and thinks they should try out the wedding on their own: a dry run with no people or cameras around to make them nervous. Chuck: "Practice makes..." Sarah: "Perfect. We'll be ready for anything."
But they couldn't have prepared for this. Close-up of Sarah's ring as she's wheeled into the hospital on a stretcher. Chuck fills in Ellie and Awesome: the poison is Thorium. Ellie says that's a radioactive metal, not a poison and wonders the form: It was liquid. Ellie asks Awesome if he has any ideas, but he says poison guns aren't in any textbooks. They put Sarah in a tub of ice, which helps her for now. But Ellie and Awesome need to know everything about this poison. And they need an antidote. Morgan comes in and joins everyone else who's gathered (Casey, Chuck's mom...). He says he told everyone at the rehearsal that it was food poisoning and she'd be all right. Then he wonders if that's true. Chuck holds her hand when she wakes up a little and tells him he looks worried. He lies that it's about the wedding, and she tells him: "Don't freak out." They talk sweetly until she drifts off again, at which point Chuck tells Casey they have to break in to the maximum security prison that Volkoff's in and get him out; he's their only hope.
Prison break. Casey and Chuck, disguised as guards, make their way in with the help of Mary back at Castle, who's guiding them and shutting off alarm systems along the way. But when they get to Volkoff's cell, the door's open. Not a good sign. And he's gone. When Chuck asks Casey where he is, a voice tells Chuck "He's gone, Bartowski." Mary wonders what's going on. Casey says he knows that voice and he goes pale, which worries Chuck more than a little. Casey asks Chuck if he remembers Casey telling him about the guy who they'd hire to put a bullet in all their heads without breaking a sweat? "This is the guy they hire to kill that guy." Chuck turns to a TV monitor in the cell (convenient!) to find Richard Burgi, a CIA guy named Decker, who tells Chuck that his CIA resources are revoked for breaking in. Chuck tells him he needs to save Sarah, but Decker has no sympathy. "Stand down or get buried." Chuck says no, and uses a chair to smash the TV. He turns to Casey and says, "That guy might think he's a hard-ass, but I'm the Intersect." No room for the Cake opening this week; too much good stuff to pack in.