‘The Diplomat’ Stars Explain Finale Cliffhanger & What It Means for Season 4 (VIDEO)

[Warning: The following contains MAJOR spoilers for The Diplomat Season 3 finale.]

The Diplomat Season 3 is must-see TV. The drama picked up in the immediate aftermath of Season 2’s massive cliffhanger, which showed Vice President Grace Penn (Allison Janney) becoming POTUS after the sudden death of President William Rayburn (Michael McKean). Fast-forward to The Diplomat Season 3 finale (Episode 8), and we have another big cliffhanger ending that sets the stage for Kate (Keri Russell) and Hal Wyler’s (Rufus Sewell) relationship to have a serious geopolitical impact next season. Where does The Diplomat go from here? Russell, Sewell, Janney, and Bradley Whitford break down the ending and tease what’s to come in The Diplomat Season 4.

The Diplomat Season 3 premiered in full on Thursday, October 16, on Netflix. The fallout from Grace’s secret attack on the British aircraft carrier reverberated throughout the season. Per Kate’s suggestion, Grace pinned the attack on the deceased President Rayburn. Callum Ellis (Aidan Turner) later revealed that a nuclear weapon called the Poseidon was on a Russian submarine that was submerged 12 miles away from the English coast. In his anger over “Rayburn’s” betrayal, U.K. Prime Minister Nicol Trowbridge (Rory Kinnear) hatched a plan to work with China to remove the submarine. Grace warned that this would be handing a nuclear weapon to China on a silver platter. They proved that Poseidon was real by secretly sending U.S. drones underwater to photograph the vessel that was geared to carry a nuclear weapon.

Hal gave Kate an assist to convince Trowbridge to work with the U.S. instead of China to retrieve the weapon. She convinced him by saying no country should have Poseidon, and he should instead accept the U.S. military’s help to bury it under the sea. But Poseidon was stolen before they could get to it, seemingly by Russia. Kate figured out in the finale’s last seconds that Grace and Hal had the weapon stolen.

“You used me to sell a lie to the prime minister,” Kate said to Hal, with whom she had just romantically reconnected. “When the Brits find out, they will consider this an act of war. So will the Russians.”

The season ended with Hal warning Grace that Kate figured it all out. How much is Kate blaming herself for not catching on to Hal’s moves sooner?

“Like all women, probably a lot,” Russell tells TV Insider. “At the initial point of impact, I think it’s just a gut punch, so I think it’s still figuring it out, but probably a lot, and that she’s let herself get wrapped up in it again, but who knows where it’s going to go from here? We’ll find out.”

Clifton Prescod / Netflix

Does Kate fear that her feelings for her husband pose a real danger to the world, now that he’s the vice president? Russell teases, “Might be a big topic for next season!” When it comes to how betrayed Kate feels by Hal in this moment, Russell says it all depends on “how far ahead [he was] thinking,” adding, “that’s where the gray lies.”

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TV Review: 'The Diplomat' Season 3

“I think she’s going to feel like he used her, but we’ll find out,” she notes.

Sewell maintains that Hal didn’t use Kate. Rather, he was given a “50-50” decision to make with POTUS, and “There is no choice that does not have dire consequences for people who do not deserve it.”

“The question I asked myself is, what other way could he have done it?” Sewell tells us in a separate interview. “And I don’t believe there is another way that he could have done it. It’s just a question of, then, what do you do? I think he just said, We’ll worry about this later, but this is a matter of preservation of the order of the world, geopolitics, geopolitical history for the next thousand years, possibly.”

“I don’t think if you game it out, there is another call that you could make that wouldn’t risk screwing it up,” Sewell adds.

Creator, executive producer, and writer Debora Cahn confirms that The Diplomat Season 4, which starts filming soon, will pick up in the aftermath of this finale revelation. Janney says that Grace and Hal are “excited by each other’s minds” and are bonded by their decision to make this “nefarious” move together, but the Kate of it all will be an issue moving forward.

“I think they see through [the nefariousness] and see the greater good of their decision,” Janney says, “but I think Kate realizes what’s happening between them at the end and what they’ve done. That shows you right away that she’s not on board with it. And I see her as a potential troublemaker to what we’re doing as a team. And it’s trouble for Season 4.”

Todd Penn (Whitford), Grace’s husband, hasn’t figured out the truth as of the finale, but he suspects something is going on between Grace and Hal. Should Todd find out what they did next season (and we’re guessing he probably will), Whitford teases how he would react, giving a sense of how this foursome could be at odds in Season 4.

“He’s clearly capable of disagreeing with the decision, but it would be in the service of supporting her, I believe,” Whitford says. “He’s clearly a guy who is in the unfortunate position of being deeply in love with a brilliant, complicated woman. And I don’t think that baseline of their relationship would go away, but I think within that, they can tangle.”

Learn more about The Diplomat Season 3 in the full video interview above, including how Cahn, Janney, and Whitford felt about staging a West Wing reunion.

The Diplomat, Season 3 Streaming Now, Netflix