Throughout the movie Esti Kuperman (Rachel McAdams) is shown wearing a wig. This wig is called a sheitel and is worn by some Orthodox Jewish married women in order to conform with the requirement of Jewish law to cover their hair.
Rachel Weisz told ScreenCrush in April 2018 that she specifically sought out this role. After spending a career acting opposite male leads, the she wanted to tell a story about female connection and sexuality. What made this project so special for her was the ease of creating chemistry with Rachel McAdams, and how the two shot one of the best sex scenes in years without even removing their clothes. She pointed out that director Sebastián Lelio storyboarded every move of that scene. "Basically in the script he wrote, 'They make love.' And that was it. We didn't really know what it was going to be. About two weeks before we started to shoot it, he presented Rachel McAdams and myself with a storyboard, which had every gesture, like my face; everything that you see in the sex scene, it was storyboarded. None of it was our idea, it was all his idea. So we signed off on it and went, 'Okay, that sounds great,' and had time to think about it. I don't know what you do with that information, but time to process it unconsciously or something. But on the day, I guess we felt safe because we knew what was required of us. We had to hit these points, and then we could abandon ourselves to doing our jobs, which was to feel. It was very vulnerable, very emotional. I've never done a sex scene that's that full of emotion and longing and needing and release and desire. It was the culmination of many, many years of waiting. It was emotional, very emotional."
Rachel Weisz said, [about costar Rachel McAdams] "We really had each other's backs and that's a form of love, I guess. I couldn't have done this with anyone else."
Director Sebastián Lelio on how he remembers his first encounters with Rachel Weisz and Rachel McAdams: "The first day with both was a milestone. I was nervous because, deep down, I did not know if there was going to be chemistry between them. I was at the end of a restaurant talking to Rachel McAdams and from afar I see Rachel Weisz walking. She sits down and they start talking. Immediately I realized that there was going to be tremendous electricity between them. The fact that they were so different was going to work perfect for the game of attraction and magnetism that the movie demanded. From my perspective, seeing them both was a sort of epiphany. I saw there was a movie, it was going to be vibrant and urgent. I realized that it was going to be tremendously powerful to watch the acting duel between them."
Director Sebastián Lelio on how different Rachel Weisz and Rachel McAdams are: "The first sensation I had when working with Rachel Weisz was that I was facing a force of nature, someone of volcanic personality. On the other hand, Rachel McAdams is very meticulous. She studies a lot and is something like an expert in disguise, hiding behind the wig and makeup. It seems to me that, in the end, [McAdams] handled all the complexities of her character with an unique elegance. They are very different and fit right into the characters, who are complementary and counterparts at the same time."