Wavy-­haired and theatrically dirty, Maslany spoke in Sarah’s lower-class British accent between takes. (She kept it up until they broke for lunch.) She was warm and self-­assured and modest and frank. She exuded a contagious ease. In our very first conversation, we bonded over the unsung virtues of the adult onesie. “I had one that had the butt-­flap until after high school,” she told me. I was as charmed as I was suspicious. Was it just another performance? Or an admission that she would prefer to be covered up?

Great acting is as much about destruction — selective, temporary self-­annihilation — as creation, so it’s fitting that “Orphan Black” starts with a suicide. Sarah happens to see a woman throw herself off a subway platform, and when she catches a glimpse of the woman’s face, she sees that it’s identical to her own. We quickly learn that Sarah, along with several other women, are clones — products of a long-­running clandestine corporate experiment. And all of them are in danger.

The clones eventually join forces, which means that Maslany winds up playing as many as four characters in one scene. These performances weren’t just a revelation to audiences; they astonished people close to Maslany. Frazee, recalling one of the first multiple-clone scenes he shot, said, “I remember thinking, [the clones] are so different, we probably could have gotten away with different actors who look similar.” He shook his head and added, “I couldn’t see, at all, the same person.” Stephen Lynch, the show’s makeup artist, told me that he is often asked what prosthetic piece he uses for a particular clone’s nose. (The answer: none.) Once, Maslany’s mother was on set watching her own daughter and wondered aloud when Tatiana would be back.

Nominally the story of how the clones find one another and team up to fight an escalating series of threats to their autonomy, “Orphan Black” grapples with the violent intersection between technology and female agency. In the eyes of their creators, the clones’ humanity is trumped by their value as intellectual property. The question at the show’s heart is whether the clones have free will and the right to lead normal lives, or if they are valuable only as experimental subjects to be monitored, impregnated, sterilized and policed. “It’s so thematically connected to feminist issues,” Graeme Manson, one of the show’s creators, told me. “Who owns you, who owns your body, your biology? Who controls reproduction?”

Because this sisterhood arises among the clones, Maslany not only had to convincingly play against herself on-screen, but also had to portray the fluid, complex, evolving relationships between her various selves as the series developed. The technical challenges were major, the shooting schedule exhausting — she is in almost every scene, often two or more times — yet the emotional work was particularly rough going.

“I didn’t sleep, really,” Maslany said of the first two seasons. “I just was shifting. I’d have to do shifts during the day where I’d be Cosima for the first half and then Helena — or whatever, Cosima and then Sarah. So my body was physically shifting in my sleep, and I could feel it.”