Watch: Gillian Anderson talks dark roles and her true crime obsession
The 54-year-old star said she sought out darker material in her free time when her day job became lighter than it had been earlier in her career.
"I've only really got into true crime since I've been doing comedy. I've been doing comedy for the past four years or so," Anderson told Yahoo UK while promoting new Gothic thriller The Pale Blue Eye.
She added: "Before that I was only just doing serial killers and really creepy stuff and I couldn't take any more, but now I'm obsessed with true crime."
Anderson is now attempting to scratch that itch for something darker with The Pale Blue Eye, which isn't a true crime tale but is certainly a story of mystery and murder.
Based on a 2003 novel, it's an 1830s-set whodunnit in which a veteran detective (Christian Bale) is summoned to investigate a killing at a military academy, where he meets a young Edgar Allan Poe (Harry Melling).
Anderson said: "It's really fun to be in this kind of world and particularly the way that one knows that [director Scott Cooper] shoots. You get a sense of it on the monitor, with the widescreen and the snow and the cadets. It was just delicious to be a part of."
Anderson plays the mysterious Mrs Marquis in the movie, with Toby Jones playing her doctor husband and Lucy Boynton as her daughter Lea, who forms a romantic bond with Poe.
"It's such an exciting genre because I think you go into it knowing that everything is not going to be what it seems," said Boynton.
She added: "I think that's the joy of it — being technical about what the audience are going to see on their first viewing versus their second viewing.
"I think that's the kind of joy of, as Scott our director keeps referring to it, dropping the breadcrumbs so that it's enough to lure you in to the first viewing and then have a dawning moment the second time you watch it and realise what it all meant."
But when she's not dealing with violence — either at home or at work — Anderson is keen to return once again to the world of Sex Education.
Season four of the show is set to debut in 2023, with the closure of Moordale School causing many characters to depart and others to be scattered around the world.
Anderson said the appeal of the series lies in its originality, saying "nobody had seen anything even remotely like it before" on TV screens.
She added: "It has so much heart to it and I think anybody on the planet can see themselves represented on screen in it, or a situation that they identify with in some way. So I think it has got a little something for everybody."
The Pale Blue Eye is available to stream on Netflix UK from 6 January.
Watch: Trailer for The Pale Blue Eye