Piper Perabo and Nic Bishop Piper Perabo and Nic Bishop

Did he or didn't he?

All signs — you know, like a floor plan layout in a bunker — point to McQuaid (Nic Bishop) being the mastermind behind the Chicago facility bombing on Covert Affairs. But in the closing moments of last week's episode, he convinces Annie (Piper Perabo) that he was framed and she lets him go — after which she lies to Auggie (Christopher Gorham) about being in contact with him.

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On Tuesday's midseason finale (10/9c, USA), we'll know for sure who is behind Chicago and "get a deeper understanding of the whole plot that has driven this Season 5," co-executive producer Matt Corman tells TVGuide.com.

Here are five things to expect from the finale:

1. Who's the traitor?
The bomber's identity will be revealed before the first act is over. So, is it McQuaid? He did talk Annie into listening to her gut last week, which hasn't steered her wrong... yet. "Her instinct is telling her that there's more going on and that instinct is serving her well over four and a half seasons and continues to do so," co-executive producer Chris Ord teases, adding that Annie, deep down, didn't truly believe that McQuaid was behind Chicago despite the overwhelming evidence. As such, she tries to help him clear his name on Tuesday's episode.

Perabo says that she and Bishop, who will be on the show the rest of the season, rehearsed the scene of Annie letting McQuaid go for a long time to strike the right balance of her conflicted feelings.

"She doesn't put the gun down, but she doesn't shoot and she lets him leave," Perabo told reporters on a conference call. "And it was all these tiny increments of, if you really trusted him you'd put the gun down and help him with whatever he needed ... so how do you kind of work in that gray area and how do you not cross the line with somebody so that you can never go back and they can never trust you? ... How you act in that scene and how you treat each other starts to set up their whole relationship for the last seven episodes."

Watch an exclusive sneak peek of Annie and McQuaid's covert (heh) meet-up from Tuesday's episode:

2. RIP ______
"Everyone will pay the price," the promo teases. Well, one person will pay with his or her life! "There will certainly be a death of a character that fans have come to know," Corman says. Is it the bomber... or someone else?

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3. Can Auggie handle the truth?
Annie and Auggie's trust issues will get a new wrinkle when he learns that she lied about McQuaid. But will he be quick to forgive again? Between her heart condition and the Paris debacle, this is her third strike. "I don't think she ever likes lying to him. But I think they both realize that in the world of espionage, truth is kind of a fluid thing," Corman says. "They've both lied to one another in the past for various things. I think in his heart he realizes that it's a mission-sensitive thing and she's not doing it to be hurtful."

4. Look who's back!
Joan (Kari Matchett) and Calder (Hill Harper) hit a wall while looking into Roger's intel files and turn to a familiar face for help.

5. Launch forth into the back six
If you think the Chicago case is wrapped up after the midseason finale, you're sorely mistaken. "We're past the prelude and we feel this episode sends us on our way into a new chapter of the same story," Ord says. Setting things up for takeoff is the climactic scene in Tuesday's episode, which requires a team effort. "The mission and what McQuaid's being folded into — it's so big, it's not just Annie that can handle it," Perabo says. "So, that's one of the things that got me really excited about the mission ... is that you need everybody. Even when we shot it we were all like, 'Yes, the band's back together,' like it was really fun for everybody to do these giant scenes together."

(Additional reporting by Kate Stanhope)

Covert Affairs airs Tuesdays at 10/9c on USA. See why else you should watch below: