The forurth season of 'Chuck' has been a head-scratcher for many of its most ardent fans. Much of what made them fans of the show in the first place -- its humor, how everyday geek Chuck Bartowski (Zachary Levi) tries to balance the spy world and his personal life, the presence of the Buy More crew -- is still there. But those aspects aren't as dominant as they once were; in some ways, 'Chuck' has shown more resemblance to more straightforward spy shows like 'Alias' this season than the funny, charming, comedy/spy hybrid that we saw in its first two seasons.

That notion hasn't been helped by the current story arc, where Sarah Walker (Yvonne Strahovski) goes deep undercover in the dark organization of Alexei Volkoff (Timothy Dalton) in order to extricate Chuck's mother (Linda Hamilton) from her 20-year undercover mission. In the meantime, Casey (Adam Baldwin) is in critical condition from a bad fall he took at the end of last week's episode. It's a dark turn for the show that many of its fans -- including our recapper, Ryan McGee -- have been hoping ends soon.

If co-creator Chris Fedak is to be believed, those fans will be satisfied with what happens during tonight's climactic episode. "It's not as if we've set some something where we're going to spend seven episodes with Sarah inside (the Volkoff organization)," Fedak told me last week. "We have bigger things that are just about to happen."

In fact, Fedak and his 'Chuck' partner, Josh Schwartz, promise that tonight's episode will be one of the most "epic" 'Chuck's ever: "Monday's episode is huge. We were interviewed, and Josh said -- and I agree with him -- that the last act of episode 13 is maybe one of the best acts we've ever done.

"It's an amazing combination of the spy world, the emotional, and Chuck's family life coming together in one amazing act of television. It's just incredible."

Yes, he used the word "amazing" twice in that sentence. But from the previews, the episode promises to be as huge as Fedak says it will be, with Chuck confronting Volkoff with the help of his buddy Morgan (Josh Gomez). At the same time, Chuck's pregnant sister Ellie (Sarah Lancaster) and her husband Captain Awesome (Ryan McPartlin) get involved, and we hear Ellie exclaiming "My water just broke!"

Just like last year's 13th episode, which signaled the real start of Chuck and Sarah's relationship, it feels like we're getting a season or series finale in the middle of the season. That's not an accident, said Fedak, as both this year and last they wrote toward the initial 13-episode order that NBC gave them. "The good thing about having 13 episodes is that you tell the story aggressively, and I kind of like that," he said. "There's no padding, there's no extra, you know, 'We're going to sit on this story for a couple of weeks and tell it at our own leisurely pace.' We move the story."

Fedak describes next week's 14th episode as a "launching pad" to the second-half story arc. He won't say much about it beyond the fact that John Larroquette will return as CIA lothario Roan Montgomery next week and that down the line Sarah will re-encounter the members of her old team, including Carina (Mini Anden). In addition, "We just finished an episode that had Lou Diamond Phillips as our bad guy. He was fantastic, really fun to work with."

But has the magic gone from 'Chuck' already? In the show's first two seasons, viewers went along for the ride with Chuck as he tried to manage the Intersect that was downloaded into his brain by his old friend Bryce, all the while trying to navigate the spy world using his awkward social skills and extensive computer knowledge. In the meantime, he was falling for Sarah. Now, he's a full-fledged spy, he and Sarah are a couple, and Chuck can kung fu like an expert. Where's the sense of wonder?

When I asked Fedak if he missed those days, he said he did, but he was also excited to see the characters continue to evolve. "There's got to be a point where Chuck becomes a little better as a spy and Morgan gets a girlfriend," he said. But the second half of the season will see more situations where Chuck leans on his own smarts as much as he leans on the Intersect.

"Chuck isn't Superman," Fedak said. "He's still a super-smart guy, and his most important aspect isn't the Intersect in his head, it's his brain. It's his smart-spy, smart-guy abilities. [He's] the guy who can disarm a bomb with computer pornography, and we want to explore that more. Going forward, we want to make sure that we're always thinking of the Chuck solution to a problem, along with the fun kung fu / wish-fulfillment side of the story."

It was exciting for the writers to explore Chuck's new "powers" during the third season and the first half of the fourth season, but "we don't feel the necessity to have the whole show culminate in a fight. I'd much rather come up with How does Chuck figure his way out of this problem? because that's what makes him unique."

The folks at the Buy More, though, especially the creepy dynamic duo of Lester and Jeff (Vik Sahay and Scott Krinsky), balance out the heavy spy stuff. Because many of the episodes this year either de-emphasized the Buy More -- now a pure CIA operation -- or eliminated it altogether, the show took on a heaviness that hadn't been there before.

Fedak acknowledged that there's something missing when we don't see the Buy More for a few episodes in a row, but there's little danger that the Burbank crew will disappear. "I think that if we did many episodes where we never fall back to the Buy More or come back to their stories, that the uniqueness of the show would fall away, because the 'Chuck' show has always been about a guy who doesn't want to give up his personal life, he doesn't want to give up his family, he doesn't want to be James Bond."

It sounds like Fedak and Schwartz know that the show's gotten a bit dark and heavy and want to bring elements of the early seasons back. Whether they can or whether this is a bell that can't be unrung is something we'll see in the second half.

One thing that will satisfy fans, Fedak promises, is that Chuck and Sarah are still a couple for the time being. "We're not particularly interested in breaking them up," he said. "Doing a wrenching tale of Chuck and Sarah falling apart as a relationship isn't exactly the thing we're excited about because we like them together as a unit. We like them as spy partners."

In fact, they're due to get closer, as Chuck was about to ask Sarah to marry him before she entered the Volkoff organization. In our conversation, Fedak referred to Sarah as Chuck's fiancée briefly before correcting himself and saying she was his girlfriend. Could that status change tonight? If it would, it would be pretty "epic," right?

'Chuck' airs Mondays at 8PM ET on NBC.

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