Politics, nuclear weapons, diplomatic crises and a high-profile marriage that always seems to be one argument away from divorce, Netflix hit The Diplomat has packed a lot into three seasons.
First aired in 2023, the drama follows Kate Wyler (Keri Russell), a career diplomat who is unexpectedly appointed US ambassador to the UK just as an attack on a British warship threatens to spark an international crisis.
What has followed – from assassination plots and secret military operations to a dead US president and plenty of political manoeuvring – has turned the show into a must-watch political thriller.
Balancing high-stakes international crises with sharp dialogue, humour and the often chaotic relationship between Kate and her husband Hal (Rufus Sewell), the show also boasts a strong cast of complex women in positions of power, including Allison Janney as US President Grace Penn, Nana Mensah as White House chief of staff Billie Appiah and Ali Ahn as Eidra Park, the CIA station chief in London.
The show has also been a critical success, with Russell earning three Emmy nominations for her performance as Kate, while Janney won for her role as Grace last month.
Season four picks up after a finale that left Kate facing a very different political landscape – with Grace in the White House and her own husband now vice president.
Before the series returns on October 15, here is a refresher on what happened in the first three seasons.
What is The Diplomat about?
When the series begins, Kate is preparing to become US ambassador to Afghanistan – the kind of difficult assignment she relishes – when an attack on the British aircraft carrier HMS Courageous kills 43 sailors and threatens to trigger an international crisis.
Instead, President William Rayburn (Michael McKean) sends her to London as US ambassador to the UK. Unknown to Kate, however, the White House has another plan for her. Vice President Grace Penn is expected to leave office because of a scandal involving her husband, and Kate is quietly being assessed as a potential replacement.
There is another complication: Hal. A brilliant but notoriously meddlesome diplomat in his own right, Kate's husband struggles to remain in the background while her career takes centre stage. Their marriage, already on the brink of divorce, is further tested when they arrive in London as separating their personal and professional lives becomes nearly impossible.
The story so far (spoilers ahead):
What happened in The Diplomat season one?
Much of the first season revolves around discovering who attacked HMS Courageous. British Prime Minister Nicol Trowbridge (Rory Kinnear) initially suspects Iran, but Kate helps prevent an immediate military response as evidence instead points to unseen Russian mercenary Roman Lenkov.
At the same time, Kate grows close to British Foreign Secretary Austin Dennison (David Gyasi), while deputy chief of mission Stuart Hayford (Ato Essandoh) prepares her for the possibility of becoming US vice president – a job she initially has little interest in.
The investigation takes Kate and Austin to Paris, where she learns Britain plans to assassinate Lenkov rather than capture him. Realising his death would prevent him from revealing who hired him, Kate begins to suspect Trowbridge himself was behind the attack.
Back in London, Hal is due to meet Conservative MP Merritt Grove (Simon Chandler) when a bomb planted in Grove's car explodes. Stuart and his aide Ronnie are caught in the blast, with the season ending before their fates are revealed.
What happened in The Diplomat season two?
Season two picks up immediately after the explosion. Hal and Stuart survive, although both are injured. Ronnie does not.
Kate's investigation eventually leads to Margaret "Meg" Roylin (Celia Imrie), Trowbridge's former political adviser, who was involved in hiring Lenkov's group to attack HMS Courageous. But Trowbridge himself did not order it.
Instead, Kate discovers the plan originated with US Vice President Grace Penn, who believed the attack was necessary to protect US national security interests.
The revelation leaves Kate believing Grace will have to leave office and, after previously resisting the idea, she finally accepts that she wants to become vice president. Hal decides Washington needs to know and, rather than going through the usual channels, calls President Rayburn directly to tell him what Grace has done.
But shortly after learning the truth, Rayburn dies – making Grace Penn president of the US.
What happened in The Diplomat season three?
Season three begins with Grace sworn in as president, leaving Kate and Hal in the unusual position of knowing she was behind the HMS Courageous plot.
But rather than distancing herself from the Wylers, Grace brings them closer – and in a major reversal, it is Hal, not Kate, who becomes vice president.
Kate remains in London as their marriage continues to fall apart and begins a relationship with intelligence operative Callum Ellis (Aidan Turner).
A new crisis emerges when a Russian submarine carrying a Poseidon torpedo – described as a "doomsday weapon" – is discovered off the English coast. When the weapon later disappears, Kate realises Grace and Hal may have secretly taken it. When Kate confronts Hal, he tells her to tell no one – then immediately informs Grace that Kate knows.
Season three ends with Kate and Grace's husband Todd (Bradley Whitford) watching their spouses together, as Kate faces the possibility that the president and her own husband have secretly taken possession of a Russian nuclear weapon – an act that could push the US towards war.
What to expect in The Diplomat season four?
Netflix says season four begins with a catastrophic event that threatens the fragile peace between the US and UK, while Grace and Hal's attempt to steal Russia's most powerful weapon risks pushing the US towards war.
It also creates an unlikely alliance between Kate and Grace's husband Todd, as they join forces to try to stop their spouses.
Janney and Whitford have been promoted to series regulars for the new season, alongside Mensah as Billie Appiah.
The Diplomat season four premieres on Netflix on October 15
