Grace Penn arrives in England for one last attempt at an agreement with Prime Minister Nicol Trowbridge. The atmosphere, as always, is thick with tension, vanity, and hidden agendas. Hal, increasingly exhausted and resentful, finally asks for a separate room — claiming he’s unwell — and suggests that Kate share hers with Callum. Offended, she refuses. But, as always, one argument is enough to make her change her mind.

Meanwhile, in another room, Grace and her husband are interrupted mid-sex by CIA agents — they thought she was being assaulted. The scene, straight out of a dark comedy, ends with Todd admitting the obvious: he’s jealous of Hal. And, generally speaking, Grace only laughs when she’s with the vice president. (Which, frankly, isn’t far from the truth.)

In yet another room, Trowbridge distracts himself with his wife, while Kate and Callum try to maintain a façade of professionalism, though the tension between them simmers. During the leaders’ meeting, the spouses are sent on a diplomatic outing — and Kate takes yet another hit: Dennison appears, now married. The look on her face says it all.

The meeting between Grace and Trowbridge quickly derails. Grace shares with him the classified information that Callum passed to Kate, and the British PM erupts, assuming it’s a bluff. He refuses to believe that a Russian submarine armed with nuclear warheads is stationed near the U.K.
Sensing the stalemate, Hal suggests that only one man can convince him — and Kate immediately turns to Callum, who, in turn, accuses her of being manipulated by Hal.

At the formal dinner, the circus escalates: Hal keeps up the façade of a happy marriage while Todd’s jealousy toward Grace becomes increasingly transparent. Callum suddenly interrupts the dinner to announce that he’ll do what Kate asked — even if it costs him his life. Hal, upon learning this, scrambles to stop him. Todd, now fully paranoid, reaches the inevitable conclusion: something is going on between Grace and Hal.

After the social chaos subsides, Hal confronts Kate privately: why does she keep sabotaging her own happiness? If she loves Callum, why not admit it? Her answer is — of course — far too diplomatic to make sense. Kate proposes that the U.S. send a submarine into British waters to capture photographic proof of the Russian sub’s existence. In other words, to deliberately provoke an international incident. Her specialty.

While Hal tries to convince Grace to approve the plan, Kate shares one last conversation with Dennison — now definitively out of her reach. He confesses that his marriage was inspired by the Wylers’ failed reconciliation and urges her to be patient with Hal. (Good luck with that.)

Grace, out of options, approves the mission. The photographs confirm the presence of the Russian submarine — but Trowbridge, naturally, refuses to believe it. Hal urges Kate to persuade him, and she does, whispering in his ear — in the series’ signature seductive-diplomatic style. But, as always, nothing stays under control: Callum discovers that the submarine wasn’t armed. The entire operation was a bluff.

Meanwhile, Todd — consumed by jealousy and paranoia — plants the final seed of discord in Kate’s mind, trying to convince her, as he believes, that Hal and Grace are having an affair. But she sees beyond it: they’ve orchestrated everything together.

The final revelation is apocalyptic — literally. Kate realizes that Hal and the president have stolen the Russian nuclear weapon.

End of season: a bitter kiss, a marriage rekindled out of convenience, and the promise of a possible Third World War. Congratulations, Kate Wyler. Diplomacy has never been this destructive.