Swarm is one of those shows that defies expectations at every turn. That philosophy applies to its tone, which switches between bleak horror and dark comedy at a moment’s notice. But it also applies to the thriller’s cast.

Created by Donald Glover and Janine Nabers, Swarm follows one young women who becomes unhealthily obsessed with a pop star by the name of Ni’Jah (Nirine S. Brown). It’s basically “What if Beyoncè’s Beyhive fully lost control?” Though the queen herself doesn’t make an appearance in the Amazon Prime Video series, Swarm is hiding one giant star. Here’s everything you need to know about Billie Eilish‘s acting debut as a soft-spoken and instantly unnerving cult leader.

The music star only appears in one episode — Episode 4, “Running Scared.” Eilish portrays Eva, a woman Dre (Dominique Fishback) meets while trying to see Ni’Jah at Bonnaroo. Dre first encounters Eva’s friend Cricket (Kate Lyn Sheil) at a gas station. After noticing a police officer harassing Dre, Cricket scares him off and insists that Dre come stay with her and her friends. The more time Dre spends with Cricket and the rest of the women, the more she realizes that this isn’t just a nice group of friends. It’s a borderline cult filled with wellness hikes and self-affirming meditations.

Eva offers Dre several free therapy sessions. If you’ve seen even a minute of this series, you know it isn’t long before that nice offer descends into a dark and darkly funny nightmare. Eilish excels at portraying her creepy cult leader. She plays the role with enough sincerity and intensity that you immediately enter Dre’s headspace enough to wonder if this woman is just a nice ally? Or is she something far more sinister?

Nope. She just gives therapy sessions and unnerves Dre with her piercing blue eyes.