Netflix released the official Season 4 trailer on Sept. 15, and Kate wastes very little time confronting what happened at the end of the previous season. Hal and Grace secretly pushed through an operation involving one of Russia's most dangerous weapons without informing their British allies.
Kate knows. More importantly, she understands exactly what the partnership between her husband and the president could mean if neither of them is particularly interested in restraint.
The season belongs to four people
Creator and showrunner Debora Cahn has framed the new season around Kate, Hal, Grace and Todd. Two marriages that once looked like separate parts of the story are now becoming tangled in the same political problem.
Grace and Hal are developing the increasingly powerful alliance that alarms Kate. Meanwhile, Kate finds herself working with Grace's husband Todd, played by Bradley Whitford. He has his own reasons to question what the president is doing and even starts moving into Kate's professional territory in London.
It is an unusually neat setup for The Diplomat because the show's political and marital storylines no longer need to take turns. Every professional decision made by this group has the potential to become personal almost immediately.
Grace Penn is comfortable with risk
Allison Janney returns with Grace now firmly occupying the presidency, but the office has not made her noticeably cautious. The trailer has Kate challenging the administration over a covert military move that could damage the relationship between the US and UK.
Chief of Staff Billie Appiah has a particularly concise answer when Kate says the operation crossed a line: the line moves.
Kate and Hal are somehow still working on the marriage
The political confrontation does not mean the Wylers have finally given up on each other. Kate explicitly says that she is trying to get back into the marriage rather than escape it, preserving the strange emotional engine that has powered the series since Season 1.
That task was complicated enough when Hal was merely an ambitious diplomat. He is now vice president of the United States and working closely with a president whose appetite for risk appears very similar to his own.
Keri Russell and Rufus Sewell return as Kate and Hal, with Janney and Whitford forming the other half of the central foursome. Ato Essandoh, Ali Ahn and Nana Mensah are also back.
October 15 picks up the damage
The Diplomat returns to Netflix on Oct. 15. Season 4 picks up with the fragile US-UK relationship under pressure while Grace and Hal's actions threaten to push the crisis much further.
Kate's unlikely answer is an alliance with Todd. Two spouses attempting to contain the political ambitions of the people they married sounds less like conventional diplomacy and more like The Diplomat operating exactly where it likes to be.
