India, Sept. 15 -- The Diplomat is heading into its most dangerous chapter yet. Netflix has released the first trailer for Season 4 of the political thriller, bringing Keri Russell's Kate Wyler face-to-face with Allison Janney's President Grace Penn as a secret involving Russia's most powerful weapon threatens to push the United States toward war.

The new season picks up with Kate dealing with the fallout from the previous season while her already complicated relationship with husband Hal Wyler (Rufus Sewell) takes an even darker turn.

The trailer wastes little time revealing that Hal and Grace have been working together to steal what Kate describes as an apocalypse weapon from Russia. "You stole it," Kate tells Hal after discovering wh...