M Night Shyamalan's acclaimed psychological thriller Servant has always walked a fine line. Tentatively balancing the harsh realities of bereavement with the undeniably surreal world inhabited by fictional Philadelphia couple Sean and Dorothy Turner, it's a series that continues to attract classic horror fans in their droves.

"It's in the writing," says Shyamalan, 51, of the show's unique tone. "There's a kind of subtlety to how we approach the genre part of it, how we approach the scares and the darkness."

A show that in many ways panders to the director's own genre-specific tastes, former Bafta and Academy Award nominee Shyamalan reflects on how Servant naturally "mimics" his personal likes and dislikes.

"When we're dealing with these kind of horror elements, they're very subtle and insinuated," says the director. "Then you can have fun with the comedy and be broad, and, you know, have a wink towards the audience."

Best known as the creative force behind hit thrillers like The Sixth Sense and The Village, Oscar-nominated Shyamalan's latest Apple TV+ project has always remained close to home, undoubtedly drawing influence from the director's own upbringing in suburban Philadelphia.

A concept created by Bafta-nominated writer Tony Basgallop (24, To the Ends of the Earth), Servant is executive-produced by Shyamalan (who also directs four episodes across all three series).

The unsettling feeling Servant exudes is every inch the tale of a haunted house turned on its head.

Featuring a grieving mother in denial, a doll that appears to transform into a living baby and a nanny with a hidden agenda, the show's premise acts as a blank canvas for mischief.

Now, heading into its third series, despite being fundamentally underpinned by tragedy, the show finally allows hope to shine through.

As celebrated gastronome Sean (Toby Kebbell) and his wife Dorothy (Lauren Ambrose) continue to live within the confines of their lavish brownstone home - this time with the addition of their newly-returned child Jericho, Dorothy's brother Julian (Rupert Grint) appears to finally be facing his own demons.

"The whole kind of dynamic is very different when we arrive at the Turners this time," says Grint, 33, best known for playing Ron Weasley in the Harry Potter film franchise.

"I mean, everything seems to be running fairly normally; the baby's back, everyone's kind of getting on as it seems and Julian has sobered up. He's not drinking any more. And he's kind of going on this fitness regime. So, yeah, things are very different."

But it's a character he's thoroughly enjoyed sinking his teeth into.

He explains: "He's very different to me personally... he's completely the opposite really. He has this real kind of confidence and bullish quality that is really fun to step into. I really enjoy embodying him. He's just always so kind of sarcastic, and he's got a great way with words, he can really use language in a great way. So I've really had fun playing him."

With Shyamalan reiterating that Servant's beauty comes from "the idea of the tragedy underneath it all", the director says Sean and Dorothy's "wonderful" relationship (despite widely being viewed as incredibly co-dependent) has grown from "this quiet mystery" into something "more buoyant".

Describing how viewers have "really responded" to the dark humour of the show's characters, the director says Servant's draw has become increasingly clear to see.

"It's a very high-stakes situation that's becoming physical," says Shyamalan.

"There's this woman that hasn't yet remembered what's happened to her family and everyone is spinning around her, trying to keep it so that that moment never happens - [that] is the engine, I think, that draws you back."

As Shyamalan continues to reflect on the nuances of Sean and Dorothy's fantasy world, Grint's co-star Kebbell, 39, is quick to acknowledge that, positives aside, series three sees his character still "very much in his fantasy".

"Series three, for Sean, is about hoping he's reached the point where he can actually just be okay and leave things to their natural chaos, rather than the exaggerated version that's been going on."

Noting his character is "still not facing the truth" in regard to the blurred lines between fact and fiction, Kebbell says the experimental chef is "still hoping that there's some kind of miraculous magic going on. And that's okay. That's fine. It's miraculous, it's chemistry, right?"

And it's this 'chemistry' that has kept his character Sean, staying loyally at Dorothy's side despite the horror unfolding since the first series when viewers learn of the death of their first child.

"Whether he's co-dependent or whatever he has, which is a similarity to Julian, he just has that thing where, if that's not real, then what has he done any of it for? Because it's so hard to do that first year of infant life and then have that stripped away.

"And the more I read about these parents - who've been found guilty, and then gone to jail and had all these awful, terrible things happen and then gone to jail, and then you realise, when they're talking about it, how they can't really comprehend that it even occurred.

"That it's too big to even really grasp. So that thing of being in love with Dorothy is just the only thing he can hold on to because if he loses her, then he'll eventually crumble, so it was a great thing to play. He's a stronger person than I am, which is great to play.

With the fourth and final season of the acclaimed show already announced, Servant's trajectory was predetermined long ago according to Shyamalan.

"I knew from two years ago, I guess, where we were going to go," recalls the director.

"We've written six of the 10 for the next season and four are fully outlined. You know, things do change, but we've been pretty accurate. When you see season three, those are the 10 beats that were written on the board a year and a half earlier. The same thing for season four.

"I think audiences, when you're asking why they're responding so strongly, it is rare that a show has figured itself out at an earlier stage," adds the director.

As for Shyamalan's lasting feelings towards Servant, the director says that in spite of the show being a "big gift" that he will "miss so much", the time-consuming nature of the project should never be underestimated.

"I didn't know I was going to do all of this; put in every sound effect and colour everything and improve everything and hire everybody and be there and do it at this level," gestures the director.

Going on to describe how he approaches projects "from a place of worry", Shyamalan says that despite having "30 episodes that are excellent, I want 40. I want to be able to sit here in front of you a year from now and go 'now I'm at peace'."

The third series of Servant is available to stream on Apple TV+ from January 21.