The Diplomat Season 4 trailer: Kate Wyler takes on White House gone 'over the line'

The new trailer for The Diplomat Season 4 shows Kate Wyler confronting President Grace Penn over a covert military incursion. The preview signals a worsening US-UK crisis as shifting alliances strain both power and marriage.

Kate Wyler has spent three seasons navigating diplomatic crises, political games and a marriage that refuses to stay simple. Now, she may have to take on all three at once. Netflix has released the full trailer for The Diplomat Season 4, and Keri Russell’s Kate is facing perhaps her most dangerous problem yet.

President Grace Penn (Allison Janney) and Vice President Hal Wyler (Rufus Sewell) have secretly joined forces over a powerful Russian weapon, with their actions threatening to push the US towards war. Kate, unsurprisingly, is not taking it quietly.

The trailer opens the door to an increasingly tense relationship between Kate and the Penn administration. She questions whether the White House has crossed from risky politics into something far more dangerous. “Your tolerance for risk to human life seems higher than it was,” Kate tells Grace.

The response from White House Chief of Staff Billie Appiah (Nana Mensah) is chillingly simple. Kate points out that the US has carried out a covert military operation in an ally’s territory and says, “It’s over the line.” Billie’s answer? “The line moves.” And that appears to be the problem Kate is going to spend much of Season 4 trying to solve.

The new trailer also puts Hal firmly back at the centre of Kate’s troubles. The couple had been trying to repair their fractured marriage, but Hal is now Vice President and has become part of Grace’s secret plan. Kate discovers that the two have been working together without telling her, putting her in the awkward position of having to confront both her husband and the president.

There is also another marriage entering the mess. Bradley Whitford returns as First Gentleman Todd Penn, who begins getting involved in Kate’s world and her diplomatic role. As Kate and Hal struggle to figure out their own relationship, Todd and Grace are dealing with problems of their own.

Showrunner and creator Debora Cahn has described the season as being built around Kate, Hal, Grace and Todd. She compares the two couples to people trapped together on a crumbling roller coaster, with their personal relationships becoming tangled up with their public positions.

That makes the fourth season as much about marriage as it is about international politics.

The fourth season brings back Russell, Sewell, Janney and Whitford, with Ato Essandoh, Ali Ahn and Nana Mensah also returning. Debora Cahn continues as creator, showrunner and executive producer.

The Diplomat Season 4 will have eight episodes, all arriving on Netflix on October 15.