There is a lot about Bloodline that makes the show hard to imagine working on network television.

In its first series, the Netflix show, produced by Sony Pictures Television, stretched to 13 episodes. The near hour-long running time of each one contains slow-burning drama that unfolds without the constraints of ad breaks (and accompanying cliffhangers).

The programme’s fixation with setting and atmosphere, the breathing space the characters are given, the cinematography and mood that switches from blinding sunlight to forebodingly dark stormy nights, is made for long, attentive viewing.

By the third episode, nearly three hours in, the characters, their lives and their relationships are established, and then the show takes hold, a thriller that offers more than a traditional family drama set-up.

Kyle Chandler, Ben Mendelsohn, Linda Cardellini, Sissy Spacek and Sam Shepard, among others, star as members of the Rayburn family, who own and run a hotel in the Florida Keys.

When the black sheep of the family, Danny (Mendelsohn) returns, old schisms and secrets are reopened, all while another brother, John (Chandler), a sheriff, investigates the deaths of Jane Does pulled from the surrounding ocean.

Family tree

Bloodline was created by Todd A Kessler along with his brother Glenn, and Daniel Zelman, who also created Damages together. Todd wrote the second and third series of The Sopranos, and that sense of a meandering but all-relevant family tree permeates Bloodline.

From the woozy harmonica opening of the show's title song, Bloodline revels in its location. "Ninety-seven in Key Largo," a muffled weather report on a television in the hospital says. Pathetic fallacy is everywhere, and the oppressive heat of islands dangling off the southern states leaves you looking for condensation on your screen from the humidity.

In the much more temperate climate of an air-conditioned hotel room in New York, Linda Cardellini and Sissy Spacek are talking about series two, all 10 episodes of which will be available on Netflix from May 27th.

Cardellini is serious and on-message, both a scholar and a sales rep for the show. Spacek is genial and freewheeling, and pleased that someone with a "Saoirse Ronan accent" is asking the questions.

Spacek – iconic in Carrie, Oscar-winning in Coal Miner's Daughter – is now in her mid-60s, and is one of a generation of older actors who are finding second, third, and fourth winds in this golden age of television. She and Shepard are perfectly cast as the Rayburn matriarch and patriarch.

There are some excellent performances in Bloodline – Mendelsohn is hapless and menacing, Shepard is fragile and unforgiving – and although the initial set-up is that of a prodigal son, this feels like Cardellini's show.

She has featured in Freaks and Geeks; a whopping 128 episodes of ER as Samantha Taggart; and nine episodes of Mad Men. But in Bloodline, the subtlety and confidence of her performance as Meg Rayburn – a lawyer with a cavalier attitude towards fidelity, whose striving in the interests of her family sometimes places her on crumbling moral high ground – is excellent.

But back to the Florida Keys. “The heat and the water and the bugs and the things that make it so beautiful also make it difficult physically,” Cardellini says of the shoot.

“That, on top of the intense drama, puts you in this place that is not your typical place to shoot a show, so you feel the weight of the humidity and you feel the weight of the scene, and you definitely feel the weight of the heavyweight actors, and it informs everything. The geography informs the intensity of the drama.”

At the outset of Bloodline, there are none of the neck-breaking twists that occur so often in contemporary television. Details of the story – embedded in flashbacks and flash-forwards – were kept from the actors.

“It just comes at you,” Cardellini says, referring to the drip-feed of revelations.

“I called it the year of not knowing,” Spacek says. “It’s challenging, but invigorating,” she pauses to laugh, “in a disturbing way.” That challenge stayed with Spacek. She says she “took Sally [her character] home, and I didn’t want to take Sally home”.

Throughout filming, Cardellini says, “We all try to pretend like we have an idea of what’s going to happen. We all have theories of what’s going to happen; 98 per cent of the time we’re wrong.

“We think we know something and think it’s heading in a direction and then it takes a turn, which is sometimes fun and sometimes you’re lost. The great thing is we rely on each other, and who better to rely on than the actors that we’re in the company of.”

This deference makes Spacek do an exaggerated and cute “Oh you!” act with her costar, but you can sense Cardellini’s sincerity.

Spacek rightly refers to Bloodline as more like an "unwieldy long movie" than a traditional television show. And the delivery of that show – all at once through Netflix – makes sense of its form.

“The way I watch television has changed: not even how we make television, but how I watch,” Cardellini says. Spacek says in this “completely new medium” of television, she’s been learning “like a kindergartener”.

“Is it streaming? Is it TV? It’s sort of a new frontier,” says Cardellini. “Film is television and television is film. I feel like it’s an interesting playground.”

Spacek has an easy solution to dealing with the format of Bloodline's new playground: "I watch it all in one day."