What happens when three couples are asked to confront their relationship problems in a room full of strangers? In Blow the Horn, director Nacho Arenas adapts Matías del Federico’s play Bajo Terapia into a tense, dark drama about relationships, communication, and the secrets people keep from one another. The couples are portrayed by Tracee Ellis Ross, Ken Leung, Lake Bell, Joshua Boone, Wrenn Schmidt, and Dallas Roberts. When they arrive for what they expect to be a therapy session, they discover that their psychologist is nowhere to be found. Instead, they are left with a letter and a series of envelopes containing questions that gradually push them to reveal more than they might be comfortable sharing.

I spoke with Nacho Arenas about adapting the play for an English-speaking audience, working with the cast to bring the characters and their complex relationships to life, building tension within Blow the Horn’s contained setting, and keeping audiences guessing until the very end.

It was definitely a very gripping watch. I had no expectations because I didn’t know much about the movie, so I went in completely blind, and I was blown away. What made you want to adapt Bajo Terapia for an English-speaking audience?

Nacho Arenas: There are two reasons I wanted to make the film. One was personal, because I grew up on the outskirts of Paris. My parents were Spanish immigrants, and I had a great childhood with a lot of love, but also a lot of tension and anxiety. There was miscommunication. There was verbal, psychological, and physical violence that came into it.

Everything was cloaked. So, when I came across the play by Matías del Federico, I thought it was interesting to really see the power dynamics in couples. It was something I could relate to because I lived through it. I think a lot of us have lived through this to a certain extent, so I wanted to adapt something that was close to those themes and try my hand at it.

The second reason was simply that I feel there are two types of films, both entertaining. One offers escapism through comedy or some type of action, thriller, or horror. Then the other one holds a mirror to someone, to an audience member, to the audience in general, and deals with real themes and hardcore issues.

Those [films] allow you to basically reflect on your own life. Even though you stay entertained, you can now start asking and saying, “Okay, I see myself in this,” or, “I see my parents. I see my friends. I see my siblings. I understand.” I think we need those movies, and independent films often offer that mirror to society that I think is important. The latter was the reason I wanted to do Blow the Horn.

It’s very interesting because you’re expecting a resolution by the end, since there are three couples. Then you start seeing the way Beth reacts to everything, and you know something is wrong. You start to think, “Something is very, very wrong,” but you don’t see any resolution.

It’s also very visceral. Seeing her be so scared, I react to it too, and you can see it in her behavior and his behavior. How did you bring that to life with the actors?

Nacho Arenas: I think the credit goes to Wrenn Schmidt and also to Dallas Roberts, who played Robert in the film. I think they had a certain communication, and they made the decisions to understand those dynamics in couples like this, without wanting to spoil anything, especially about the ending.

There’s a certain behavior, there’s a certain structure, and there’s a certain power dynamic within that couple that predetermines the way the spouse reacts to a situation: how she shuts down and how she gets emotional about things. To me, it’s important once you watch the film, and maybe if you have the opportunity to watch it again, you realize how every single envelope, every single beat, is a trigger that leads to the resolution at the end.

But I wanted to keep it playful in such a way not to let the audience really know which couple is in trouble. Every single envelope allows you to focus on a certain couple and their relationship, so by envelope six or seven, you’re confused about which couple is the one that’s going to go, and why. Then the twist at the end just blindsides you, and that’s for the audience to react and see how they feel about it.

It’s also interesting that the two male characters opposite Robert are different: one is open-minded and progressive, and the other is closer to him. It kind of brings out who he is.

Nacho Arenas: That’s the beauty of Matías’ play, and what I wanted to keep: honor the text and also honor the dynamics. What we feel is left to impromptu.

The reading of the envelopes and answering, it is actually very, very calculated by the couples. We wanted one to be a little more reactive to Robert, whereas another one is trying to get closer to him so that he feels like he has an ally. That’s what happens in envelope eight, when he says, “I thought we were friends,” and the other says, “We’re not friends.” And that’s the reality of things. That’s when I wanted the walls to close in, the tension to rise, and the anxiety to be greater, so that when we hit you with the twist, it’s really gonna blindside you. That was the fun part of it.

It definitely did. The film is essentially built around this very contained premise: just three couples in one building. How did you approach making it feel cinematic and visually dynamic rather than theatrical?

Nacho Arenas: Well, thank you for saying that. A lot of credit goes to Dina Goldman, our production designer, and to the communication and collaboration she had with me, and that I had with Jeffrey Kim, our cinematographer, who’s fantastic. Then the choice of space… We knew it was going to be one room, so we faced the challenge that it could be boring or it could be visually unstimulating if you have the camera still and if you stay in the same place for an hour and a half.

We wanted to use the space and have the actors travel within that space and create different scenarios and different dynamics that would absolutely keep the viewer engaged. Hopefully, it will lead the audience to be in an active mood rather than passive, because it’s just one room.

Dina Goldman did a phenomenal job dressing the room, which was challenging because it’s a lot of windows, and we shot day going into night. Then the cinematography, Jeffrey, and the crew… Honestly, I was blessed with not just the actors but a fantastic crew that was able to help me do as great a job as I could.

And how did the casting process influence the characters? For example, did someone audition for a certain role, or did that change when you saw their audition and thought they might be a better fit for another character? Or did it all come together on the first try?

Nacho Arenas: No, listen, it’s not easy. First of all, because it’s based on a play, it’s a heavy dialogue, and you need to honor the text. You need to know the text.

We shot very quickly, only 17 days in Brooklyn, in the middle of winter, and it’s uncomfortable. It really pushes your limits. Within the constraints and structure of the play, and the comedy and then the drama, it becomes really challenging.

I didn’t have any specificity when I wrote the script; there were no descriptives. The first person that came in and responded to the script was Tracee, and I loved her work in American Fiction.

I think she’s a light. The moment she walks into the room, she has a smile; she’s a force of nature. I can’t speak for her, but for me, the question was: This comedic actor, this person who has a smile on her face the entire time and lights up a room, can I actually tighten and darken everything to see what her performance would be like? She was terrific in American Fiction.

Then Ken came on. His career started some 25 or 30 years ago, and people know him from Lost and, I think, Rush Hour. A lot of people now know him from Industry. This was a challenge. He reacted to the script pretty quickly and he loved it. His process was totally different from Tracee’s, and different again from Joshua Boone’s, who plays Richard.

It was fun for me to see them play with one another. No one auditioned. It was a meeting, a conversation I had with each of them. Then you have a gut feeling and say, “Okay, I think this fits. This goes in.”

I was grateful. There’s a great diversity and a great mix that made sense and felt natural.

I can see why they were so attracted to the script, because you made a really good movie, and it’s one of my favorites this year. It came out of nowhere, and I’m happy to see it and happy to talk to you. 

Nacho Arenas: Demet, thank you so much for giving me those minutes. I appreciate it, and I’m grateful that you watched it and liked it.

This interview has been edited for clarity.