IT BEGINS like any other morning: Samuel and Janet are walking dogs on a bleak, windswept beach in Yorkshire. The sky is overcast, the wind biting. They exchange some routine pleasantries. But when Samuel's white Pomeranian runs over, barking, with its beard soaked in blood, he and Janet's lives are irrevocably tipped upside down.
The strangers discover a fishing trawler washed up on the beach, and with it, two dead bodies and a haul of cocaine. Their spur-of-the-moment decision to snatch the illicit cargo entangles them in a web of deceit, mafia retribution and murder – one they may not escape alive.
BBC One's six-part darkly comic thriller, Boat Story, treads the tightrope between violence and humour, relatability and absurdity. It is the directorial debut of brothers, screenwriters and producers Harry and Jack Williams, the duo behind The Missing and its spin-off Baptiste.
The Williams brothers have called it a "primal story". It continually circles back to the dilemma at its core: Do you take the cocaine or leave it? Where does that decision sit on the morality scale? And what factors tip the balance?
Paterson Joseph and Daisy Haggard take the lead as Samuel and Janet, respectively. The stellar lineup also includes The Thick of It's Joanna Scanlan, Baptiste's Tcheky Karyo – as sinister mafia boss, The Tailor – and Rise of the Footsoldier's Craig Fairbrass. Most of the cast have worked with the Williams brothers before. All are glowing about their abilities.
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"So many episodes just took me completely by surprise," says Joseph (59) known for Peep Show and Noughts + Crosses. He'd receive an episode and think "oh god".
"It's really exciting to open a script and feel like even I don't understand what's about to happen. There's also just surprises that are designed to f*** you up. So their scripts are really just marvellous – to work on something that feels like you're being surprised by yourself."
For Scanlon, it is that they never stop working on the story – it is "constantly changing, in flux, from their point of view, during the shoot and in the edit as well".
"Their laser focus on creating as many twists and turns for an audience is quite unusual," the 62-year-old continues.
"I've never worked with writers who are so prepared to be creative, really, genuinely, massively creative during the shoot. So I think they're very brave and they take their own line and they give us actors a lot of fun because we have to be on our toes. They see in us things we don't see in ourselves."
"Reading the scripts was really exciting because you couldn't predict it," adds Haggard (45), best known for Breeders and Back To Life.
"It was so original and exciting and fresh and thrilling. But it always felt right. It's just so great because you've always got something to play with because there's such drive and desperation that in every scene you've got this big thing driving you which is just pure terror and fear."
Both Samuel and Janet are down-on-their-luck, troubled individuals. There is a desperation that propels them both to cast their fate to the wind – but what that looks like for each of them is vastly different.
Janet has had a hard run of things by any measure: her hand was crushed in a factory accident, the result of a negligent boss who immediately proceeds to ply her with whisky for pain relief only to rob her of a payout by claiming she was drunk on the job. Her ex has banished her from seeing her son Alan.
Haggard depicts her with that fragile yet witty, bravely optimistic persona that she's refined in other roles. Janet's broken but has an irrepressible capacity to turn her life's failures into a joke.
Samuel harbours a secret gambling addiction: one that's robbed him of his life savings and forced him to uproot his family to evade bailiffs. He is manic, wide-eyed, drowning in duplicity.
"I've had a very vague experience with gambling," shares Joseph, "only a moment when I was like 17, where I definitely made a decision not to do that.
"It's in my family so I know what it's like. But the thrill of it, that's what's exciting for gamblers – the absolute risk, the edge you're taking yourself to before you plunge. And when it's gone from your life you need something else.
"It was good to have that engine behind what Samuel did, the decisions he's making. That's not something that I would do. I look at all the consequences and go, it's not worth it, however much money this might be. Whereas he's got that gambler thing, going, 'Yeah this could be it.'"
"Janet is somebody who is at such a low ebb at the beginning of the show, everything that could possibly have gone wrong in her life has gone wrong," says Haggard.
"But she is still one of those people who will make a joke or try and laugh, especially for Alan. It's sort of a really sweet love story of a mother's love and she does this wild thing and makes this crazy decision, but it's for him. And who she is means there's humour along the way because that's how she sees the world."
Every character grapples with demons. Each, to some extent, deals in shades of grey. No-one is quite what they seem.
On the face of it, Scanlan's character, local woman Pat, is an ordinary note in an otherwise extraordinary tale. A mother, and former paramedic who's reinvented herself as a pasty maker with a little shop of her own.
"I thought that when we started," Scanlan explains, "but actually things happened in the process which I sadly can't reveal at this moment, that completely twisted that around.
"As an actress, it was something very, very surprising for me. Extremely so. It wasn't what I signed up to do."
Boat Story comes to BBC One on Sunday November 19.
