The Diplomat Finale Recap: A Shocking Betrayal Leaves Kate (And Us) Stunned — Plus, Grade The Season!

We're used to big twists on "The Diplomat" — but we have to admit: We didn't see this one coming.

Season 3 of the Netflix thriller wrapped up with a finale that sees Kate and Hal join Penn and Trowbridge for a tense summit after Trowbridge publicly blamed the late former President Rayburn for the attack that killed 41 British sailors. Things are tense between the spouses, too: Hal gets a separate bedroom for Kate in case she wants alone time with Callum, while Todd is jealous of how close Penn and Hal are getting. To make things even more awkward, Dennison has brought along... his new wife! (Oh hi, Tracy Ifeachor from "The Pitt"!) 

Penn tries to tell Trowbridge he has a Russian submarine off his coast carrying a dangerous nuclear weapon, but he doesn't believe her and walks out on the meeting. Kate turns to Callum, asking him to share his Russian intel with Trowbridge. But that would expose Callum to criminal prosecution, and maybe condemn his source to death. Callum eventually agrees, but Hal nixes it, urging Kate to come up with something else. And she does: She hatches a plan to send an American sub down to take photos of the Russian sub and show that it has a modified hull, proving there's a nuclear warhead onboard. They'd normally need permission from the UK... but Kate tells Penn to just do it first and then ask for forgiveness later. Piece of cake, right?    

After Kate and Dennison share a warm moment by a warm fire — are we sure these two are still just colleagues? — Hal gets Penn on board with the plan, and Kate tells a grateful Callum he doesn't have to sacrifice himself. The two delegations sit down for a meeting, and Penn shows Trowbridge the photos of the Russian sub that prove it has nuclear cargo. (She says they sent an underwater drone to take them.) She offers to send American forces to take out the sub, but Trowbridge flatly says no. He can't believe she broke his trust again by entering UK waters without permission. It seems like all is lost until Kate gets in Trowbridge's ear and tells him to bury the Russian sub in concrete on the ocean floor: "No one should have it." He seems to like that idea, and he and Penn shake on it. So do we have a happy ending? Yeah, about that...

Kate tearfully apologizes to Hal for the whole Callum thing, falling into his arms: "I'm so sorry. You have to forgive me. You have to take me back." He assures her, "I'm still here," and they kiss. (Nothing like forging a peace treaty among superpowers to heal a marriage.) She's ready to head back to D.C. with Hal when Callum tells her the Russians must've taken the nuclear weapon, because sensors indicate it's no longer aboard the sub. Kate tells Hal, and he goes to confer with Penn as Todd asks Kate if she's bothered by their "extremely productive working relationship." Kate laughs him off... but then a look of realization crosses her face.

She pointedly asks Hal if the Russians took the weapon, "or did you two?" She points out that Penn told Trowbridge they sent an unmanned drone, when she knows they sent a sub capable of handling that weapon. "You made a secret plan with somebody last night," she says to Hal. "Was it me or her?" He insists the UK and Russians won't find out they took the weapon, even though if they do, it could mean a disaster of global proportions. "Kate," he coldly tells her. "You will tell no one." He goes back to talk more with Penn, telling her, "She knows," and Kate's jaw is on the floor — and frankly, so is ours.

Whoa... once you've picked your jaw up off the floor, give Season 3 of "The Diplomat" a grade in our poll, and hit the comments to share all the intel you've got.