The Diplomat Showrunner Explains Kate's Big Decision in the Season 4 Finale

[Warning: The following contains spoilers for the Season 4 finale of The Diplomat, "Warships." Read at your own risk!]

The Diplomat's Kate Wyler (Keri Russell) is the United States ambassador to the United Kingdom no longer.

By the end of the fourth season of Netflix's The Diplomat, Russell's whip-smart yet unpolished protagonist — who also happens to be the Second Lady — decides that she can no longer serve in the presidential administration of Grace Penn (Allison Janney), whose escalating erratic behavior turns into a thinly veiled declaration of war on the international order.

At the start of a G7 Summit in Tuscany, Italy, Grace unexpectedly delivers a matter-of-fact address in front of the assembly of international delegates. Shortly before the summit, newly minted British Prime Minister Bethan Vaughn (Jodie Whittaker) guaranteed safe passage into U.K. waters for Russian search crews to retrieve a missing submarine — which contained a nuclear-powered weapon known as the Poseidon — that had ended up several miles off the northeast coast of England. The issue, of course, is that Grace and Vice President Hal Wyler (Rufus Sewell) had already covertly deployed an American submarine to steal the nuclear weapon for themselves.

Rather than covering up the illegal operation, Grace confesses to the delegates that the U.S. intervened and stole the weapon from the Russian sub. She frames these aggressive moves as necessary, unilateral actions required to protect British citizens, European security, and NATO territory — and notably dismisses Vaughn's handling of the situation as a grave security risk. But in her most chilling declaration, Grace asserts that the U.S. will actively shoot at any nation — including its own allies — that tries to interfere with its self-appointed mission to stop Russian submarines from entering U.K. waters.

Having spent the entire season trying to manage the fallout of the stolen warhead and watching the White House punish internal dissent from figures like Deputy Chief of Mission Stuart Hayford (Ato Essandoh) about the mission, Kate walks up to Grace to formally tender her resignation in front of the entire assembly. Kate's walkout then influences three key characters to follow her out of the building: White House Chief of Staff Billie Appiah (Nana Mensah), U.S. Secretary of State Miguel Ganon (Miguel Sandoval) — and, yes, Kate's VP husband, Hal.

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Unlike the first three seasons — where she started with a rough outline and hoped her writers would elevate the plot — creator and showrunner Debora Cahn had this ending mapped out from the start. "I was scared that we weren't going to be able to justify it, but I knew exactly what I wanted it to be," she told TV Guide.

Below, Cahn explains the real-life questions of domestic policy and foreign diplomacy that informed the latest chapter of her Emmy-nominated political drama; her ongoing fascination with the "slippery" nature of personal and professional alliances — and the major creative lesson that she learned from working on Grey's Anatomy under Shonda Rhimes, who once tasked her with killing off a particularly beloved character during the show's heyday.

While The Diplomat has always been fundamentally about marriage in the world of foreign affairs, this season widens its lens to show how fragile relationships become when international alliances — and the personal bonds between diplomats on opposite sides of a border — begin to fracture. What were the animating questions that informed your approach to writing Season 4?

Debora Cahn: In a hypothetical world where somebody felt that their government was not behaving in the way that they might ultimately wish, what do you do? This is the question that I asked all of the diplomats, policy people, and everybody we interviewed at the beginning of Season 4. The Trump administration at the time had just fired 200,000 people, a lot of them being foreign service. A lot of ambassadors were fired for the sin of having experience. I asked everybody, "So what do you do if the government is making a decision that you think is unwise? What do you do when the government is making a decision that you think is maybe illegal? What are your choices?"

Throughout the season, what you see is a roadmap of the answers to that question: "How do you object internally? How do you consult with other people you respect and see if they have the same point of view and concern? How do you try to embrace the idea that not everybody's going to like every decision?" Everybody in government is really, really passionate, but at a certain point, the decision gets made and you get on board and suck it up. [Either] you say, "I am going to do something that might get me fired," or "I'm going to do something that crosses my own moral and ethical lines, but just because we don't like it doesn't mean we can let go of it." It's the government; a lot of people depend on it. [But] when do you resign?

It feels worth pointing out that those questions also came up during the first Trump administration, when you were first mulling over the idea of this show after working on The West Wing and Homeland.

Cahn: In the first Trump administration, we were able to see how some people handled it. Some people decided that this was the line that they were not going to cross and they were going to speak truth to power. They did it and then were fired, and they knew [their firing] was going to happen. Some people quit in protest and did so on the front page of every newspaper, and some people quit in protest with only internal dissent. So this was the season where I wanted to go through all of those things.

Throughout the course of the season, everybody — Kate, Hal, Billie, Stuart, Todd [Grace's husband played by Bradley Whitford] — is going through this process of, "I'm not sure about that presidential decision, so what should I do? How can I exert pressure? Can I get somebody who might be more influential? [We should] bring in the family." People are going to Todd and trying to utilize Todd, and Todd is trying to, on his own, figure out: Does he have any power? Is he actually the last person his wife is going to want to hear from about things like this?

We watched a lot of people resign in protest in the first Trump administration, and that did… not nothing, but it didn't stop all of this from happening again. My fantasy version is that if enough people did it, if it kind of became a moral contagion, then maybe it would have more of an impact on the public. And maybe it won't; maybe it does a fat load of nothing.

There is a huge shake-up in the U.K. government this season. Foreign Secretary Austin Dennison (David Gyasi) is killed off-screen in Amritsar, India, in a helicopter crash. U.K. Prime Minister Nicol Trowbridge (Rory Kinnear) then abruptly resigns from office after Kate effectively blackmails him with a recording of him attacking his now-dead former advisor Margaret Roylin (Celia Imrie). Vaughn is quickly introduced as his new successor and a potential foe to Kate during the second half of the season. Why did you want to introduce a new Prime Minister at this point in the show's run?

Cahn: First of all, we were in the U.K. filming on and off for about three years. During that time, there were five different prime ministers. So Trowbridge had managed to stay in office an unrealistically long period of time. [Laughs.] In Seasons 1 and 2, you're grabbing the low-hanging fruit; you're telling the most fundamental stories about the world that you're getting into.

But fairly quickly, it was clear that there was this huge part of being a diplomat that we were not addressing at all, which was the cyclical nature of it. Most diplomats change posts every three years. They're not allowed to stay in one place for very long, and in those three years, the government turns over any number of times. So you do all of this work to create a situation where you are able to have insight and communication and hopefully some influence, and then one day there's an election, and that whole thing is gone and you're starting from zero. So I wanted our characters to be facing that, because it seems like such a foundational piece of diplomacy.

I also wanted to see what happens when you're dealing with somebody who you think is irrational, unstable, reckless. Trowbridge is a bad guy. Certainly from all evidence, he's not up to the task. I always imagined Kate saying, "If he was not there and there was somebody who was reasonable and rational and like-minded, can you imagine how much we would get done?" I wanted to see that come true and have her face [this idea of], "Be careful what you wish for."

The most nightmarish part of that [idea] was, "You thought he was the problem? Well, I think you are the problem. I think you are a reckless, lawless, proto-fascist government that I'm now forced to deal with." That's Bethan Vaughn's point of view. So whenever possible, I want the story to come around to the pain that we [as Americans] have wrought in the world, as opposed to looking at another country and wagging our fingers and saying, "You're pretty tough for the United States to deal with." That's not as interesting to me as saying, "You know what? We're a real nightmare for other people."

Grace rules with an iron fist, but part of the magic of Allison Janney's performance is that you don't realize what she's doing until after she makes these big decisions that could likely upend the Western alliance.

Cahn: She's doing things that are bold and increasingly autocratic, but she always has a good reason for it. If plan B was better, she'd do it. But she feels that plan B is more dangerous; she feels that it puts the United States and its citizens in danger far more.

The character that I find most fascinating is Hal, who effectively serves as a liaison between Grace, her administration, and other world leaders. He acts as her primary check and balance — even as he maneuvers relentlessly to protect his own seat at the table. He loves this kind of access and power and clearly doesn't want to give it up easily.

Cahn: He likes the access to power, but he also likes the president. We worked really hard to make Grace Penn's argument at literally every step of this [storyline] be completely rational and understandable to people across the political spectrum — and we asked, we checked. There are things that individuals wouldn't do, but understand why in this circumstance it makes sense. The counter-argument is shared with the audience every single time. Either the president is saying herself, "I'm doing it for this reason," or somebody is saying, "Well, we're reading it like this, but one could look at it like this."

There's a reason everybody in the federal government hasn't quit. If it was so easy, everybody would've just done it. A lot of people who haven't done it have thought about it, I'm sure. I think a lot of what's stopping them is that the administration is doing a lot of things that they support. So they're prepared to swallow a lot of razor blades because the Supreme Court is doing things that they want it to do, or because there's a fiscal decision that's being made that they really support. And Kate likes this president. She thinks she's really f---ing smart and has a lot of priorities in the right place. It's not just like, "Well, she's batshit crazy and we gotta get her out of there." It's not that simple.

The Diplomat has now used its high-stakes geopolitical backdrop to dissect not one but two messy, long-term marriages — Kate and Hal, and now Grace and Todd. How did you think about further developing those relationships this season?

Cahn: We're starting the season with the connection between Hal and Grace being stronger than the connection between Hal and Kate. So a Todd and Kate alliance develops in the shadow of that, or because of that, or in order to mitigate that. I was very taken with the idea that the four of them are sort of chained together. It always makes me giggle when you see photos of the president and the first lady and the vice president and the second [lady/gentleman]. Everybody's waving and they're holding hands and you think, "Do they like each other? Can they tolerate each other?" But whatever the answer is, they're stuck together.

In this circumstance, they are discovering that they can count on each other in certain ways that they aren't sure they can count on their spouses. When you're at that level, there's so few people who you can talk to and trust. There's so few people who have any idea what is going on that it makes a lot of sense to me that you turn to people who are in the rocket ship with you. There's only four — and boy, when you're arguing with your spouse and there's this other person around who really shares a lot of the same agenda, the way that those lines of connection can shift and flip were really interesting to play with.

Kate decides at the start of the G7 Summit that she is "no longer able to support the actions of the Penn administration," so she takes off her lanyard and earpiece and announces her resignation in front of other world leaders. Can you give voice to what is going through Kate's mind as she walks out of that building?

Cahn: When Kate is walking out of that room and through that massive, cavernous ancient hall of power — which is a Medici palace that we filmed in — I think she's overwhelmed with waves of nausea. "What catastrophic, idiotic [thing] did I just do? I couldn't stop myself, but I can't believe I did that. I've now ruined everything." That's how she feels until she hears the door open and turns around and sees that Billie is behind her. So I don't think she was planning to march out and talk to the press. I think she was planning to walk out the side door unrecognized. But when she sees she has sort of started a movement, then the options change — and particularly when she started a movement that includes the Vice President of the United States.

Hal spends the season's final episodes questioning whether his and Kate's marriage was even worth saving in the first place, so that begs the question: Why does Hal ultimately choose his wife over his work, at least in this instance?

Cahn: I don't think he chooses his wife; I think he chooses right versus wrong as he understands it. In that room, Grace has basically said that she's walking away from the Western Alliance, which is a military alliance that has created the greatest period of stability in the world in recent history. [Kate] feels like it's so dangerous that she can't do it and her one voice is not going to do anything, but at least she has to at least mount this small protest in public, which is somebody saying this is not OK.

You can hear the same argument over and over and over again, and then somehow a different person says it, or they say it in a different way, or it's said in a different context, and you're like, "Oh God, I've been lying to myself. What she said is actually what I have always believed, and I've been justifying this for a lot of good reasons." Sometimes, when it's just right there flatly stated on the table, it's undeniable. So I think he responded to Kate doing that; he was being smacked in the face with the idea that they're not arguing over the nitty-gritty of policy. They fell in love with each other because they had a very strong set of shared values, and there were certain red lines that they would never cross. They've both now crossed [those red lines] miles back, and we've reached the point where there's no longer any way to defend it.

We don't know what Todd's doing when they're all outside. All we know is that when we're in the room, he's acting like he wants people to sit down, not stand up. There is something that is different about taking a stand against your boss and your commander versus your spouse. It's a different kind of loyalty, which is why people with power liked monarchies for so long.

So, should we interpret this ending as the forming of a new alliance between these four defectors of the Penn administration?

Cahn: Well, they're aligned when they're in the driveway — and that's really all we know. Alliances are slippery!

The finale ends with Kate announcing to the press that the VP would like to make a statement, but we don't actually end up hearing that speech. Did you always know that you wanted to end with that shot of Kate looking straight into the camera?

Cahn: Yes, I knew that's how I wanted to end the season.

So, looking ahead to a potential fifth season, what can you say about where the next season will pick up? Will we see the speech that Hal makes to the media?

Cahn: That's a really good question. Stay tuned, my friend. [Laughs.]

At this point, are you able to talk about your long-term vision for the series? Do you have a target number of seasons — or even an ending — in mind yet?

Cahn: I can't. I'm always happy for something better to come up, but I've always known how the series would end, and that hasn't changed in my mind.

Before I let you go, I actually wanted to ask you about one other show on your résumé: Grey's Anatomy. You famously wrote the Season 5 finale where the doctors realize that John Doe is actually their colleague, George O'Malley (T.R. Knight). Have you seen any of the viral TikToks of first-time viewers losing their minds over that twist?

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Cahn: I have not seen those videos. [Laughs.] I did not know that that existed, but that's great. What I remember about that was... Shonda is bold. She is unafraid to make a huge move in a different direction. The audience is expecting things to go over here, and she's going to swerve hard to the left. She has a relentless fealty to the dramatic narrative, and she's not wringing her hands like, "Well, the fans are going to be upset." Clearly her instincts are pretty good because now lo and behold, 42 years later, Grey's is still on the air. [Laughs.] But I remember thinking, "Wow, I can't believe we're killing George."

I know the showrunner is responsible for giving the final seal of approval on any scripts, but since your name is on that episode, you are kind of forever known for being the writer who killed George O'Malley.

Cahn: It's always terribly sad to kill off an actor. But once you've gotten your mind around the fact that you're doing it, you know that you're holding a tremendous amount of emotional power in the script because if you don't do it too often and abuse the emotional privilege that your audience is giving you, they have a connection to this character and it's going to be a big loss. One of my favorite things is writing moments that are extremely low-key and mundane that happen right before a huge dramatic moment. So the scene where [George] is drawing 007 on [Meredith's] hand was one of those moments. I haven't seen it in more than a decade, but I do remember that the conversation that precedes [the reveal that George is John Doe] is just really workday stuff and everybody's fairly calm and bored a little bit, and then this thing happens. So it's always an exciting turn to be able to take. Those are powerful episodes.

The Diplomat Season 4 is now streaming on Netflix.