CASTING SHOCKER: The Diplomat locks in Aidan Turner for Season 3 — and fans are already bracing for the political chaos ahead.

The brooding star joins Keri Russell’s high-stakes drama, with whispers that his role could upend the fragile alliances at the heart of the Netflix hit.

Bradley Whitford is not the only high-profile new cast addition to Netflix‘s The Diplomat. Aidan Turner (Poldark, Rivals) also has a key recurring guest star role in the upcoming third season of the political thriller drama. Details about his character are being kept under wraps.

Whitford and Aidan Turner join returning series regular cast members Keri Russell, Rufus Sewell, David Gyasi, Ali Ahn, Rory Kinnear, and Ato Essandoh as well as returning recurring players Allison Janney, Nana Mensah and Miguel Sandoval.

In Season 3 of The Diplomat, which picks up in the aftermath of the dramatic Season 2 finale, Ambassador Kate Wyler (Russell) lives the particular nightmare that is getting what you want. She just accused Vice President Grace Penn (Janney) of hatching a terrorist plot and admitted she’s after the VP’s job. But now the President is dead, Kate’s husband Hal (Sewell) may have inadvertently killed him, and Grace Penn is leader of the free world.

Kate steps into a role she never wanted, with a freedom she never expected, an increasingly complicated friendship with Foreign Secretary Austin Dennison (Gyasi), and an unnerving bond with First Gentleman Todd Penn (Whitford).

The Diplomat, from creator, executive producer and showrunner Debora Cahn, returns for its 8-episode third season on Oct. 18. Janice Williams, Russell, Alex Graves, Peter Noah and Eli Attie also executive produce.

The series’ second season received two Emmy nominations, for Outstanding Drama Series and Lead Actress In a Drama Series (Russell).

Known for playing the title role in the BBC historical drama Poldark, Irish actor Turner currently stars in the breakout 1980s Hulu comedy-drama Rivals, which is returning for a second season. His notable credits also include the BBC 3 series Being Human and The Hobbit movie trilogy. He is repped by Curtis Brown and Felker Toczek Suddleson.