In other words, Adelaide’s outfit functions as a window into her true identity. Observant viewers might notice the many ways in which Us uses clothing to tell the story of the Wilsons and the uprising of the Tethered. Every detail about the outfits used in the film—including the doppelgängers’ instantly iconic jumpsuit uniform—was meticulously planned by the movie’s costume designer, Kym Barrett. Best known for her work on The Matrix, Barrett thought carefully about the decision to have Adelaide wear white. “I wanted her to be the lantern that led her family,” Barrett told me recently, after she had seen the completed film for the first time. “Along the way, that light is continually flickering … She’s getting more and more and more covered in blood. The idea was that [by the film’s end], she’s almost as red as Red.”

Claudette Barius / Universal Pictures

According to Barrett, every film is rooted in a distinct psychology. The costume designer must be a psychologist who investigates the material world the characters inhabit in order to pull their deepest motivations to the surface. “You’re trying to work out why people did things, where they lived and why they lived there, and what happened to them,” Barrett said. The Australian-born designer began developing this analytical approach to her craft while working as a wardrobe designer on Baz Luhrmann’s Strictly Ballroom (1992) and as the costume designer on Romeo + Juliet (1996). In her early days designing for theater, Barrett had operated off gut instinct, feeling her way through what characters would wear. By the time she was hired as the lead costume designer on The Matrix (1999), her first big-budget Hollywood film, Barrett had learned there was a kind of science to costume design. She realized she needed to become a “method designer,” employing tactics similar to those of method actors, to better understand a film’s anatomy.

It makes sense that a costume designer whose own creative process is so cerebral would be a natural fit for a movie by Jordan Peele—a modern-day master of suspense who imbues the tiniest of details with meaning. Barrett said when she first met Peele to discuss Us, the synergy between their ideas was palpable; she was hired that same day. Her first task as costume designer was determining the psychological core of the film, and she knew early on that Nyong’o was the key to the story. “She, obviously, is the linchpin of the script,” Barrett said.

The designer and actor met for several hours in New York City, where they discussed the dramatic tension between Nyong’o’s dueling characters—two women whose bodies share the same soul, as The Atlantic’s Hannah Giorgis recently explored. “Like two good investigators, we were asking each other questions,” Barrett recalled of her first encounter with Nyong’o. The main topic of their conversation: “the tightrope between the two characters. How do you cross between the two characters, keeping them familiar but separate?” Nyong’o had the idea to develop a distinct voice for Red and a particular walk informed by trauma, which then helped Barrett visualize how the character would be clothed.

Adelaide, in contrast to Red, is always dressed in white. When she’s first introduced as an adult, she’s wearing a lightweight white shirtdress. She later changes into a cream ball cap and a white T-shirt (paired with light-khaki shorts), which she wears to the beach, before changing into her final outfit: the white T-shirt and cardigan combo. The color choice is the result of deep psychological work Barrett had done to flesh out Adelaide’s character. “She had to appear to be completely normal,” Barrett explained, adding that Adelaide picks her clothes so that the people she encounters can’t tell she’s really a Tethered. “It’s all about a neutral palette. What she chooses is really generic, and anyone can project onto it whatever they want to see,” Barrett said.