For three seasons, the Keri Russell-starring political thriller The Diplomat has contended with a universe in which the Americans have double-crossed their closest allies, the U.K., through the actions of Vice President Grace Penn (Allison Janney). In season 3, the fallout from that betrayal becomes more threatening after President Rayburn (Michael McKean) dies suddenly, and Penn is promoted to the highest office. Despite some officials knowing the truth, including Russell’s Kate Wyler and her husband Hal (Rufus Sewell)—both career diplomats—their quests for political gain are also part of the equation.
The Netflix hit’s latest season, which premiered on October 16, 2025, tests the Wyler marriage when Hal is appointed to the Vice Presidency over Kate, and again when Kate discovers his collusion with Penn during a heated international negotiation over a deadly weapon called the Poseidon in the finale. Does their marriage survive the acts of betrayal, and can the alliance between the U.S. and the U.K. ever recover? Read on to find out how season 3 of The Diplomat ends, and how it sets up its already confirmed fourth season.
