On a Toronto soundstage in February, the hit sci-fi drama Orphan Black is humming, shooting the eighth episode of its fifth and final season. Cosima (one of many clones played by Emmy-winner Tatiana Maslany) and Delphine (Evelyne Brochu) are huddled around a computer in Cosima's underground laboratory, which includes a mini grow-op. "For medicinal use only," whispers John Fawcett, an affable dude with floppy blond hair, who co-created the show with Graeme Manson.

The writers are toiling, too. The final scenes that Fawcett and Manson (who sports a shaved head and interesting eyewear) have envisioned since day one aren't working, so they're refining episodes 9 and 10. No pressure there.

An adjacent set is littered with props, wigs and costumes. Every wig has dark roots, a nod to the genetic link among the clones. Each clone has her own wardrobe rack – punky Sarah's is all black leather and hoodies; flashy Krystal's, leopard and lamé. The clothes for Helena, the most dangerous clone, are shredded and blood-stained. The costumers pull together 15 to 30 choices per clone per episode, and Maslany texts them late at night with suggestions.

Story continues below advertisement

There are retractable knives, charred Barbie-esque doll heads – Mattel declined to let the production use real Barbies – and books annotated with arcane codes. There are fake scorpions (for blocking only; during filming, a scorpion wrangler unleashed the real thing, with a dot of glue on their pincers and stingers to make them safe. Maslany was cool with them, until she realized one was on her neck). There's a rubber dead baby, chalk-white, so sad and eerie that no one wants to look at it. And on a gurney, partly covered with a sheet, lies a naked body – a full silicone cast of Maslany, so heavy it takes three people to lift it. Her eyes are closed, her hands and feet delicate.

"Oh great, my dead body is here," Maslany says, entering the set with her co-star Kristian Bruun, who plays Donnie, husband to Alison, the suburban clone. Bruun pretends to pull the sheet down. "Don't look," Maslany squeals.

Everyone's at their most gracious today, the last press push for what they all call "our weird little show." (The final season begins June 10 on Space and BBC America, at 10 p.m. ET.)

Orphan Black has been a real Canadian Cinderella story – if Cinderella had multiple, murderous clones who became tangled in an international, Big Science conspiracy.

"Nobody wanted to make this show," Fawcett says. The concept – a genre mash-up – was new. "There was not a lot of conviction from anyone that it was going to work." Fawcett and Manson, newcomers to show-running, spent 10 years developing and flogging the idea with Temple Street Productions (and its parent company, Boat Rocker Media). Finally BBC America, which was just getting into original programming, said yes. With real money in place, Canadian specialty channel Space signed on.

Orphan Black’s Donnie (Kristian Bruun), Alison (Tataina Maslany) and Felix (Jordan Gavaris).

"I think back to Tat and me, day one, scene one of shooting," says Kevin Hanchard, who plays police detective Art Bell. "We were quivering like branches on a tree." They had no idea what Maslany would be asked to pull off, and how well she'd succeed.

"That first season on set, we felt we had something – 'This is different,'" Bruun says. "BBC America, Space and Temple Street saw that as well. They trusted us and let us do our thing."

Story continues below advertisement

"The outcome – would it be a hit? – took up no real estate in my mind," Maslany says. "I was like, 'How do I get through this episode?' It was a moment-to-moment challenge."

But from the premiere, March 30, 2013, fans and critics got it, creating a synergy between audience and creators that most shows only dream of. The themes were beyond timely: identity, autonomy, feminism, diversity, inclusion, nature versus nurture, ownership of one's body. Viewers who responded to them, especially young women, found each other online, creating the Clone Club.

"They are connected to each other internationally," Maslany says. "They meet in cities to be together and talk, not just about the show, but about science and feminism and art. That blows my mind. They opened our eyes to what reach can be." Clone Club members began visiting the set; they inspired the writers and actors to double down on those themes.

"I'll be getting a coffee, someone will glance at me," Bruun recounts, "and suddenly they go weird-faced. They launch into how much they love the show, Tat, the storylines. Random people tell me deeply personal things on the street."

By the end of Season 1, Fawcett and Manson had to toss their imagined three-season arc and develop a five-season one. Awards and accolades rained down: Canadian Screen Awards, GLAAD Media Award nominations, a Screen Actors Guild Award, a Peabody. Maslany won a Young Hollywood Award in 2013, a Critics' Choice award in 2014, had an Emmy nomination in 2015 and won an Emmy in 2016 – the first Canadian lead to win for a Canadian show.

"To see Tat win was such a release for all of us," Bruun says. "Here we were, nominated against these massive, sweeping epics with big budgets and huge stars. We were on our feet screaming and crying. We were like embarrassing cousins at a wedding."

Story continues below advertisement

Maslany tries to shush him, but he goes on: "There's not a person on this planet who has a harder acting job. Tat is the hardest-working actor in the world. She preps four, five leading roles every episode. If it was just quantity, that alone would be insane. But the quality of her output – I'll never see anything like it again."

The impact of the show has gone "well beyond our best-case scenario," Manson says, in both entertainment culture and on the Canadian TV landscape. The co-production model had been used before. But Orphan Black's success with it blew open the doors for sumptuous-looking, well-written Canadian co-pros, including The Handmaid's Tale, Alias Grace and Anne – the glimmerings of a Maple Golden Age.

Boat Rocker Media is plowing its profits from Orphan Black back into Canadian television, buying animation studios, TV libraries and a stake in the New York-based digital publication the Outline, which they hope will generate stories that can be made into television. And for now at least, Maslany herself is staying in Toronto, resisting the siren call of L.A.

"I think we've made a splash," Maslany says. "In the beginning people would say, 'Oh, this is a Canadian show?' Now they know. And other things in the world are also making Canada a place of note."

Maria Doyle Kennedy, who plays Mrs. S, agrees: "I think the timing is very good for seeing a perspective of tolerance and inclusion, and for that to come from Canada. I've often heard Canadians put their own stuff down, and look for validation from the U.S. I'm from Ireland, and we suffer the same manifestations of a postcolonial idea. But this show proves that stuff that's made here is as good if not better than stuff made anywhere. It's increased confidence in the thing Canadian."

"When you're limited with cash, it limits the number of characters you have, the number of hours you shoot," says Jordan Gavaris, who plays Felix, foster brother to the lead clone, Sarah. "Your world stays small. Corners get cut. But with the right budgets, not only can we compete with American content, we can politicize our own TV. Canada is 150 this year. That's a young country, just finding its voice culturally. We're on the precipice of figuring out who we are. I hope we stay on this path of not apologizing for the fact that we have a different perspective than the U.S."

"The show became political without us really realizing it," Manson says. "Events have been catching up. We're talking about the importance of diversity on a biological level. And Tatiana's commitment to diversity, she lives it. She's politically active, and demands respectfulness around all those issues. It's wonderful how our idea about cloning – that we're all the same – has grown to encompass another idea: We're also different, and our differences are the most important thing about us, as humanity."

Orphan Black premieres its fifth and final season June 10 on BBC America and Space at 10 p.m.

Maslany is revered on set, sincerely. Stephen Lynch, the key makeup artist, extols her work ethic (though she pulls a 70-hour week, she often gives up her lunch hour to refine looks with him) and her talent – she can hold her face so it looks like fake teeth! She became a producer during the run of the show, and managed it with grace. "She's a master class in acting and interpersonal relationships," Kennedy says.

"The way Tat moves through the world as a young woman, in a business that can be oppressive, she's a unique paradigm," Gavaris says. "Her voice is in everything you see. Her leadership is never about satisfying her needs. It's about satisfying the art."

The writers credit Maslany for pushing them – for example, to broaden Helena from a generic assassin to a damaged woman with a deep backstory. On the weekend, as they laboured on the finale, she came in and worked on the story with them. "She taught me as a director to be more present, in the way the scenes go down," Fawcett says. "This is not a typical lead-actress collaboration."

The clones could have been excruciating, just wigs and mannerisms. Maslany makes them characters. "I'd mostly played opposite Cosima, and we had a banter between scenes," Brochu says. "But when Rachel walked in" – the most coolly conniving clone – "everyone's spine went up. It wasn't that Tat was 'being Rachel.' But something in her soul felt changed, and the scene hadn't started yet." She shivers. "I'd much rather play opposite Cosima."

Maslany's head still spins when clones pretend to be each other. "I always start with the clone I am, and play to the opinion she has of the other clone, which is usually judgment," Maslany says. "But it's embarrassing. I know I'm being seen in an act. I'm caught acting." For one crazy scene, she had to be Sarah, pretending to be Alison, pretending to be Donnie. "I felt insane that day," she says.

The most challenging scenes, of course, are those where the clones interact. First there's the repetition, doing the scene over and over as one character, then another. Then there's the infinite technical finessing. The show's tech has always raced to keep up with its stories, says Geoff Scott, the visual-effects supervisor. With each new script, his heart constricts in panic. Then he buckles down and figures it out.

In Season 1, he celebrated after Alison poured Cosima a glass of wine and it was so seamless that no one noticed. By season's end, he'd pulled off a clone dance party. "That was us showing off – 'Please, somebody notice!'" he says, laughing. Season 4 ended with an epic fight between Sarah and Rachel – one stabs another in the leg – in which Scott "Frankensteined pieces of Tat and her double, Katherine Alexander, using the legs from one shot, the torso from another." It took 20 compositors hundreds of hours to pull off.

Scott and his team have developed new tech: When they needed a camera mount that would repeat its movements identically so the takes would match, they found robotic factory arms too noisy. So they built their own super-techno-dolly. But Scott also embraces low-tech: He blocks scenes using dolls on his desk. Effects experts on other shows routinely call to ask how he did something or other. He always shares. "I don't believe in secret knowledge," he says. But he's learned to not shoot clone scenes outside – the simplest ones take two days, and weather is too changeable.

Despite the bustle, it's clear the series is winding down. (The final shoot date is a month away, March 21.) The cast and crew are in that bittersweet, last-days-of-high-school place, simultaneously looking backward and forward. "We're starting to get wistful," Bruun says. "Lots of crying at read-throughs."

"Lots of group texts about how much we love each other," Maslany says. Tonight, the cast will go out for beer, pizza and dancing.

Rachel, the most coolly conniving clone, talks to Sarah, the main clone on the show, both played by Maslany.

They agree it's time to go. "How long can you string an audience along?" Bruun asks. "People want the answers." They're relieved they're going on their own terms.

"We have a sense of finality," Hanchard says. "The writers are working with purpose and intent. The actors can drive for something. It's only 10 episodes, so it's like water going into a funnel, it gets faster and faster."

"Everyone has their favourite clone, and Graeme and I really wanted to use this season to explore those characters more deeply," Fawcett says. "Like, who are Cosima's parents?"

Manson concurs: "We're happy we have this space to ask, 'Who were they when we met them, and who are they now?' We get interesting answers."

"Five seasons is a great run," Maslany says. "We don't want to start repeating ourselves." She gets offered a lot of twin parts. She's not taking them any time soon. "Character is the thing I'm most turned on by," she says. "This show has such a strong external aesthetic. I'm excited to do more subtle, internal character work, where I don't have to wear a wig and do an accent." She's done four films during Orphan Black's run, and two are Canadian indies: Two Lovers and a Bear, directed by Kim Nguyen; and The Other Half, directed by newcomer Joey Klein, co-starring her partner, Tom Cullen.

Maslany does have one mandate, however: "I've had my eyes opened to the deep need for feminist stories on TV. That's something I want to take into all my future work. Tell stories about the true nature of where we're at, in terms of what needs to change."

As the day ends, Fawcett takes a spin around the sets. Some have changed this season. For example, Rachel is undergoing some spiritual growth (they call her "Enlightened Rachel"), so she has a meditation room – though its gleaming white perfection is still pretty scary. Felix has temporarily converted his loft into an art gallery; there's a painting of Rachel on the floor, so people can dance on her face. But Alison's craft room, with its rolls of ribbon in rows like soldiers, is unchanged. "There's so much responsibility – to the characters, the story, the fans," Fawcett says. "We want to get everything right. I hope we manage it."

He can't imagine what a sixth season would look like. "We have nothing left," he says. "It would be the clones sitting around playing board games." Beat. "I think some people would still watch that, though."