'Black Bag' starring Michael Fassbender, Pierce Brosnan mixes marriage and espionage

Michael Fassbender and Cate Blanchett play British spies George Woodhouse and Kathryn St. Jean in new spy drama "Black Bag"

They both work at an organisation where a traitor is scheming to steal top secret technology.

The married couple of top intelligence agents have their loyalties tested in the movie which also stars James Bond actor Pierce Brosnan.

Expert interrogator George gets tasked with finding the mole and discovers his wife is among the five potential culprits. He rounds up the suspects, played by Naomie Harris, Rege-Jean Page, Marisa Abela and Tom Burke, at his house for an evening of "fun and games" aimed at eliciting information from the group of professional deceivers.

"The core of the story is actually where does George's loyalty lie? Is it to his wife or his country?" Fassbender said at the film's London premiere on Tuesday.

"It helps when somebody is doing the same job as you in understanding what it's all about. Obviously, it's heightened in this scenario because it's espionage," said Fassbender, who is married to actress Alicia Vikander.

Blanchett said: "The research we did is so few people who work in espionage are able to maintain and sustain a relationship. All that stuff's there in the movie."

A black bag is the term the operatives use to refer to information they cannot divulge to anyone, their partners included.

"Black Bag", which was written by David Koepp and directed by "Traffic" and the "Ocean's" movie trilogy filmmaker Soderbergh, features more dialogue than action, adding a theatre-like quality to the London-set project, Page said.

"I think this film is primarily concerned with the human cost and the human impact of spying," said Page, known for his performance in television series "Bridgerton".

"It's very much about how can you trust anything when you lie about everything? How do you carry that in a relationship? It goes in pretty deep on that," Page, who plays Colonel James Stokes, said.

"Sitting across the table playing this kind of verbal, psychological tennis game...there is no weak link in this incredibly high-quality cast."

"Black Bag", which also stars Pierce Brosnan as the head of the spy agency, begins its global cinematic rollout on March 12.