Peter Capaldi and Jessica Raine on Amazon thriller The Devil's Hour

Written by newcomer Tom Moran, it’s an unsettling psychological thriller with shades of whodunnit, domestic drama and horror. Lucy Chambers (Jessica Raine), a child protection officer, has a fraught relationship with her son Isaac (Benjamin Chivers). Withdrawn and emotionally blank, the eight-year-old’s condition defies diagnosis and Lucy’s estranged husband has all but given up on him.

Equally distressing are Lucy’s daytime visions and the nightmares that wake her regularly at 3:33am, in the middle of the so-called 'Devil’s Hour', when the space between the living and the dead is supposedly most porous. These visions draw Lucy into the orbit of both Capaldi’s nomadic loner Gideon, the prime suspect in a series of murders, and an odd-couple pair of coppers, played by Nikesh Patel and Alex Ferns.

Sitting down to talk at the drama’s production base outside Farnborough, Raine and Capaldi are both dressed in character – she neat and groomed in a trouser suit, he wild-haired and a little dishevelled.

Raine describes Lucy as "a gift – partly because she’s a well-written character, but there’s also a Sliding Doors element where you see a different path taken. She’s not this perfect human being, but you love watching her make those decisions and mistakes. Her visions are getting so bad that she’s questioning her own sanity, but aside from that, she’s the most relatable character I’ve ever played. She’s a warm person and doesn’t take herself too seriously, but she’s absolutely shattered and on the edge of coping. We all know that feeling. I really admire her tireless energy in getting to the bottom of what is wrong."

Did being a mother help to access those feelings? "Yeah, definitely. Because you just don’t know until you know, do you? This all-encompassing love and fatigue and relentlessness. If I was raising a child and getting nothing back for eight years, I would really struggle with that. So for me it’s a love letter to motherhood as much as anything. I’ve found it really moving to play."

Capaldi makes his first appearance at the end of the opening episode, gaunt, imposing and enigmatic opposite Lucy in a police interrogation room. While gentle charm personified in person, Capaldi has played his fair share of monsters, most famously The Thick of It’s splenetic spin doctor Malcolm Tucker, with his "attack eyebrows".

"Gideon is a murderer and a danger to society," says Capaldi with a wolfish grin. "A cross between a crusty and a survivalist who exists on the fringes of society, always on the run. He seeks Lucy out because he believes he has some degree of clairvoyance and that she may be of significance in some wider plan."

So does Gideon have supernatural powers? Capaldi ponders. "I think supernatural is the wrong word, because it’s not about ghosts or spirits. If you didn’t know about photography, you’d think that this chemical and mechanical process was magical. In essence, Gideon is that – there is a scientific way to explain him, but just not yet. Does that make sense?"

Well, sort of. He sighs. It has been a fiendishly difficult round of press, even for a man used to keeping secrets after years at the controls of the TARDIS ("It was ridiculous – who cares if the Cybermen will be here next week?").

"I’ve never been quite in this position where you can really say nothing without giving everything away. It’s more difficult to explain than it will be to see." He brightens. "But it’s fun! I get to do lots of nasty things and wreak havoc through the whole thing."

But how relatable is Gideon? "He’s driven by a slightly fractured good-heartedness, at least from his point of view. But I never understand when people say you have to find something relatable in a character. I think that’s nonsense. If something’s well written, it gives you space because all you have to worry about is telling that story. Do you have to find something relatable about playing a pharaoh? That he likes a half-hour nap?"

Capaldi has always been a consummate napper himself ("You got an hour for lunch in the old days"), but Raine found her sleep disturbed. "I have lost the ability to sleep on this job – there was a point where I was waking up at 3:29am! It got under my skin, but Lucy has to be really tired so it was quite useful. I just loved that she was absolutely on her knees with tiredness, which I related to, with a two-and-a-half-year-old and a full-time job."

The Devil’s Hour prods at some deep philosophical considerations: the line between the rational and irrational, paths taken and rejected, fate and destiny. Is fate something Capaldi or Raine believe in?

"I believe in luck," says Capaldi. "I always think it’s a bit dumb when people say you make your own luck. I might not have been available to do The Thick of It, I could have been doing Midsomer Murders! I was lucky to grow up at a time where you could come from a very humble background and you weren’t penalised, you were supported to go into further education. It's all going backwards now, which is terrible."

Raine concurs. "There’s an old quote I love: 'Luck is where opportunity meets preparation.' That’s a good one, isn’t it? Some people just get really lucky, but I feel like I’ve worked really hard. There was zero nepotism, no one to give me a hand. Of course, there’s luck in terms of what is fashionable at the time, but it’s about making sure you’re ready for when the luck comes along."

With season 1 wrapped, Raine is hoping fortune calls once more, explaining she's in "that weird holding pattern" and awaiting news on whether the series will return (she has signed up for a further two). Capaldi will be returning to the director’s chair (he won an Oscar in 1995 for his short film Franz Kafka's It’s a Wonderful Life) – but once again, that’s as much as he’s giving away.

He’s also playing a policeman on Criminal Record, a new police thriller for Apple TV+. "You don’t realise how delicious it is to lift one of those 'Police: Do Not Cross' tapes until you've done it. That was genuinely fulfilling." He looks aghast. "But I’ve already said too much…"

The Devil's Hour launches exclusively on Prime Video on 28th October – try Amazon Prime Video for free for 30 days.

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