The Diplomat. (L to R) Rufus Sewell as Hal Wyler, Keri Russell as Kate Wyler in episode 308 of The Diplomat. Cr. Courtesy of Netflix © 2025
COURTESY OF NETFLIX
Warning: Spoilers ahead for The Diplomat Season 3.
After another politically chaotic season of The Diplomat, fans are already wondering what’s next for Kate Wyler and Hal. But it’s the final quiet moments of the finale that raise the loudest questions: Will there be a Season 4, and what could happen after that jaw-dropping twist with the Poseidon missile?
The Diplomat Season 3 begins with Vice President Grace Penn assuming the presidency after the shocking death of President William Rayburn (Michael McKean). However, one of Penn’s surprising first decisions in office is to appoint Hal as her vice president, even though Kate wanted the job, which worsens her tumultuous relationship with her husband.
“We talk about Season 3 as ‘the split,’” creator Debora Cahn told Netflix’s Tudum. “It’s the time when Kate and Hal’s relationship really falls apart. It’s the time when the US-UK relationship really falls apart.”
With Hal now Vice President, Kate resumes her role as ambassador to the U.K. They decide to stay together publicly but move toward a private divorce, allowing them to see other people. “Publicly, they’re still married. Privately, they know that they’re not, although Hal is never a give-up kind of guy,” Cahn continued. Season 3 toggles back and forth between the beginning of Hal and Kate’s relationship and the present day.
In the finale, Kate recommits to Hal and asks him to take her back. But the twist ending in the final seconds of Season 3 could change everything — and force her to question whether she knows him at all.
How Does The Diplomat Season 3 End?
The Diplomat. Rufus Sewell as Hal Wyler in episode 308 of The Diplomat. Cr. Idris Solomon/Netflix © 2025
IDRIS SOLOMON/NETFLIX
In the final seconds of Episode 8, Kate Wyler makes a startling discovery. She believes that Hal and Grace conspired together to steal the Poseidon missile, a Russian nuclear weapon of doomsday-level destruction, for the U.S.
The Poseidon was being kept on a disabled Russian submarine off the coast of England. Nicol agrees to have it covered in concrete and hidden on the ocean floor. However, British spy, Callum Ellis (Aidan Turner), Kate’s secret love interest in Season 3, tells her that the Russians found the sub and took the Poseidon.
But it wasn’t the Russians, after all. Kate pieces together that it was the Americans (Grace told Trowbridge that the U.S. sent an unmanned drone to take photos of the sub). That’s when they sent a submarine big enough to hold the Poseidon to steal it.
“It’s pretty bad,” series creator and executive producer Debora Cahn told USA Today about Kate’s predicament in the finale. Kate “is going through this experience in which her vision of who (Hal is) keeps changing and shifting. And just as soon as she feels like she understands who he is and understands who she is herself, the picture shifts radically.”
When Kate confronts Hal — concerned that the theft could lead to a war between Russia and the U.K. if the Russians think the British were behind it — Hal forbids her from saying anything. “You will tell no one,” he says. He then walks over to President Penn and whispers, “She knows.”
It’s unknown where Kate and Hal’s relationship will go in Season 4. Before Kate discovered her husband’s betrayal with the Poseidon missile, she apologized to him in an intimate moment and asked him to take her back.
“It’s great and terrible to watch Kate understand what she’s done. It’s awful when it all comes crashing down on her that she’s made such a big mistake, and she is just begging for another chance,” Cahn told Tudum. “That much clarity coming that fast is really brutalizing.”
Hal accepts Kate’s apology and promises he’s “still here.”
Will There Be The Diplomat Season 4?
The Diplomat. Allison Janney as Grace Penn in episode 308 of The Diplomat. Cr. Clifton Prescod/Netflix © 2025
CLIFTON PRESCOD/NETFLIX
Yes, Netflix renewed The Diplomat for a fourth season in May 2025. The exciting announcement was made by Netflix chief content officer Bela Bajaria on stage at the Netflix Upfront in New York City, Variety reported at the time.
“I’m so excited about Season 4,” Cahn told Tudum. “It’s going to be a lot of fun. We get to the end of a season and I always think, ‘Well, there’s no way that we can do this again.’ And then we dig back into it, and it’s like, ‘Oh my God, we have to keep going.'”
Although the third season dropped on Oct. 16, the show is wasting no time before starting Season 4. Netflix confirmed that production for the next installment begins this fall. Allison Janney and Bradley Whitford, who portray Grace and Todd Penn, have been promoted to series regulars.
What Will The Diplomat Season 4 Be About?
The Diplomat. (L to R) Bradley Whitford as Todd Penn, Allison Janney as Grace Penn, David Gyasi as Austin Dennison, Rufus Sewell as Hal Wyler, Tracy Ifeachor as Thema Dennison, Keri Russell as Kate Wyler in episode 308 of The Diplomat. Cr. Idris Solomon/Netflix © 2025
IDRIS SOLOMON/NETFLIX
The Diplomat Season 4 will pick up after the Season 3 finale, following President Penn and Vice President Hal’s shocking plan to steal the Poseidon missile for the U.S. — a move that could have grave consequences for the U.K., U.S., Russia, and the entire world.
When asked by Collider about what could unfold in Season 4, Cahn said that although the writing sometimes changes as the story unfolds, the team plans to explore the power dynamics between Kate, Grace, and Hal.
“What does it mean to have two powerful women with one powerful man stuck in the middle of them?” the showrunner said. “How do those relationships impact each other and change each other?”
She continued, “Hal is in a different relationship right now. He has a very, very potent and important relationship developing and succeeding with another woman who happens to be the President of the United States. The idea that that was not going to change the chemistry of the marriage was also magical thinking.”
Cahn also teased to Tudum that fans “should be worried” heading into Season 4. “There’s plenty to worry about,” she said. “It can be pretty chilling when you see who takes power and get the sense that they may be horrifically misusing it.”
When Is The Diplomat Season 4 Release Date?
The Diplomat. (L to R) Keri Russell as Kate Wyler, Aidan Turner as Callum Ellis in episode 308 of The Diplomat. Cr. Clifton Prescod/Netflix © 2025
CLIFTON PRESCOD/NETFLIX
Netflix hasn’t announced a release date for The Diplomat Season 4 yet. Based on the release pattern of the previous three seasons, the fourth season will likely premiere in fall 2026. Season 1 arrived on Netflix in April 2023, Season 2 in October 2024, and Season 3 in October 2025.
With production for the fourth installment already underway, a 2026 premiere date seems likely, or, at the latest, 2027. The streamer is expected to release more details in early 2026.
The Diplomat Season 3 is streaming on Netflix. Watch the official trailer below.
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