Chaplin stars as Maddy, a former army medic and wife of high-flying MI6 operative Adam Lawrence (Charlie Cox), in the recently released series.
*Warning – Major spoilers ahead for the Treason finale*
In a major twist, Treason kills off its lead star, Cox, midway through the final episode.
Chaplin told The Independent in an interview that the series’ producers had to call her while they were halfway through shooting to let her know that the ending had been changed.
“I know that they were kind of toing and froing about it because nobody really wants to kill Charlie Cox,” she said of the decision.
“But they called me and they said, ‘Okay, brace yourself. Are you sitting down? We've made a change. This is what's happening.’ And I was like, you’ve got to be f***ing kidding me. I was devastated!”
Chaplin struggled to remember the specifics of the original ending but explained that Cox’s Adam “stayed alive”. “They went for the more interesting option,” she said.
“Nobody wants to see Charlie Cox die and that's why we need to see Charlie Cox die.”
In recent years, a number of prominent action series and films have ended by killing off the hero at the end. The most famous recent example may be Daniel Craig’s James Bond in his final 007 film, No Time to Die.
“We have to check ourselves to see if we're just doing a gimmick,” Chaplin said, “because shocking the audience, just for the sake of shocking the audience, is something that I don't like. It has to have integrity within the story.
“I think they did it really well in Treason.”
Elsewhere in the interview, the actor spoke out against Russian villain tropes and gave her thoughts on the need for intimacy coordinators in Hollywood.
Treason is out now on Netflix.