Episode 10x02, "We Are the End of the World," reveals Gamma alongside sister Frances (Juliet Brett), the same Whisperer seen abandoning a baby to walkers outside the Hilltop in Season 9. As one of the most loyal acolytes of leader Alpha (Samantha Morton), Gamma sacrificed her wavering sister to a pack of the undead to save Alpha — a move that won the otherwise nameless Whisperer the distinction of "Gamma," making her just the third Whisperer to carry a title after Alpha and Beta (Ryan Hurst).
"It was a huge challenge, but also a massive reward because you're coming onto a show that's an incredibly well-oiled machine," Birch said on Talking Dead. "Everybody knows their place and everyone's got the vibe down, but also there's a huge sense of mystery for someone like me coming onto it. They're just like, 'Basically, yeah, go over there and Whisperer walk your way around this corner.' And you're just expected to kind of immediately fit in. I'm like, 'Wait, someone please tell me what to do, how to do it.' And actually Ryan was one of my besties immediately, because I'm like, 'How do I Whisperer walk?' He's like, 'Oh, you just go out there, you do whatever.' I'm like that's a great philosophy, I'll go with that [laughs]."
The high-ranking Whisperer first made an impression when it was realized she's wearing clothes taken off the corpse of the slain Enid (Katelyn Nacon), one of ten victims murdered by Alpha in revenge against the survivors warned not to trespass into Whisperer territory.
Gamma's ceremonial induction was "a huge part of one of my first days," Birch added. "Another part of my first day was actually the day where I eliminate my sister. So I had talked with Angela for a period of time about my overall arc and where it was going, but I hadn't realized I would be doing the main deed in the first episode. Unfortunately, I became too attached to the actress that was playing my sister. We had gone out a couple times and I was like, 'I'm sorry, I gotta kill you!'"
Birch notes the decision that ended with Frances torn apart by the Whisperers' "guardians" was an instinctual one for Gamma.
"I think in that moment it's very much an instantaneous decision, she doesn't even think about it. It's very much, 'My plane is going down, who do I protect? Do I protect the co-pilot or the pilot? I protect the pilot,'" Birch said. "And I think that that's very much her thought process. She doesn't even think about it. It's not even her sister on top of Alpha, ready to kill her, it's just an entity. And we have to remove that entity to protect the god."
Showrunner Angela Kang previously revealed Gamma will play a key role in Season 10.0comments
"Gamma is a character that we'll get to know in the season. I'm such a huge fan of Thora Birch's work prior to this show. I particularly love Ghost World, but she's done such amazing stuff all around and she's been a wonderful addition to the cast," Kang told EW. "She has such an interesting take on this character because when you have a group that's wandering around wearing skin masks, you have to kind of be in a particular sort of space to kind of decide, 'This is the only way that I can survive or this is the right way.'"