Chuck and Jill are at the carnival, and she asks if he likes her surprise. He tells her his tension is just his irrational fear of carnivals. She takes him to the top of the ferris wheel and it stops. She starts talking about what happens next: Chuck gets nervous, rambles on, and then she has to kiss him. She does, and Chuck either really learned from Sarah or can't help loving Jill. After the kiss, she says she's sorry, and when he asks why, we see she has a gun aimed at his stomach. Was all of that really necessary? Couldn't she have pointed a gun at him somewhere other than on top of the ferris wheel. Why did she have to ruin this sweet memory Chuck had?
After commercials, she explains she works for Fulcrum, and that they want her to kill him. He asks her not to, and she says she doesn't want to because she's not a killer. He talks her out of it, and she tells him there's a Fulcrum operative watching them, and he'll kill both of them if they see that she doesn't kill Chuck. Casey and Sarah realize that the music center Chuck GPS is a fake one, and they turn around and head toward the carnival. Jill and Chuck are trying to leave the carnival when "Leader" shows up. And, seriously, that guy's a bad guy? No one would ever suspect. He's bald, wearing a leather jacket, with a creepy moustache. He has all of the trademarks of a bad guy, so I'm shocked that's the agent. Actually, I am sort of surprised, because this show is usually a little more subtle in its choice of agents and villains. Leader looks ominously at them and cuts them off as they try to get away. He tells Jill to eliminate Chuck, but she won't do it, so Leader's going to until Jill points a gun at him. Chuck immediately takes off running, which is so much smarter than people usually are in TV and movies. Go Chuck! Leader knocks Jill out and says she's making a big mistake.
Chuck runs in to the Gravitron and Leader follows him in. The door closes and Chuck hits the on button. If you have ever ridden the Gravitron, you'll get why this is a hysterical place to set a fight sequence. You cannot even move on this ride, let alone try to fight or run away. Both Chuck and Leader are plastered against the walls. Leader manages to climb on top of Chuck, but then the Gravitron stops, and they fall down, Chuck landing on top of Leader, knocking him out. He makes his getaway. That whole Gravitron sequence was very funny, which is probably why they named the episode after it, but I think "Chuck Versus the Carnival" would have been a better episode title, since they do so much more at the carnival than just fight on the Gravitron.