EXCLUSIVE: Douglas Smith has joined the FilmNation feature Miss Sloane, which is headlined by Jessica Chastain and directed by John Madden (Shakespeare in Love). Smith, who recurs on the HBO drama Vinyl that premieres Sunday, will play Alex, a young lobbyist named who joins a coalition to try to help pass important gun control legislation. His is one of the key roles in Miss Sloane.

Others already cast are Mark Strong, Michael Stuhlbarg, Gugu Mbatha-Raw, John Lithgow, Sam Waterston, Alison Pill and Jake Lacy.

Miss Sloane was picked up by EuropaCorp at Toronto last year. Luc Besson’s company, which just replaced is CEO Chritosphe Lambert with former Uni chair Marc Shmuger, is fully financing the film and handling worldwide distribution.

The script is from first-timer Jonathan Perera and is a behind-the-scenes look at lobbying in Washington D.C. Chastain plays a woman who is considered the top lobbyist in D.C. When she decides to take on the challenge of pushing through tighter legislation for the nation’s gun laws, she soon comes to find that the gun lobby is as ruthless as she is. Through her actions (for better or worse), she unwittingly mentors a younger generation in her office. The role that Smith plays is that of one of the smarter, younger member in her office; he is in multiple scenes.

Ben Browning is producing for FilmNation and Patrick Chu is the executive producer.

Douglas recently wrapped the lead role in the STX horror film Bye Bye Man directed by Stacy Title and produced by Intrepid Pictures. Others may remember him from Terminator: Genisys or Big Love. He is repped by Paradigm, More/Medavoy Management, and Morris, Yorn, Barnes, Levine, Krintzman, Rubenstein, Kohner & Gellman.