It’s rare that filmmakers discover a fully formed script from an award-winning (and Oscar-nominated) screenwriter while spring cleaning, but few have the honor of having Guillermo Arriaga as a father. The writer is known for his collaborations with Alejandro González Iñárritu, including Amores Perros and Babel, but can now add talented filmmaker offspring to his list of accomplishments.

Mariana and Santiago Arriaga are already accomplished short filmmakers; so it makes sense to adapt a forgotten ’90s script from their father for their debut feature. Upon Open Sky (or A cielo abierto) is about two brothers journeying through rural Mexico with their stepsister to seek vengeance on the truck driver responsible for their father’s death, but it’s primarily a graceful and sensitive depiction of adolescence in crisis. Projektor talked to the directing duo at the Venice Film Festival about what they brought to the story.

Projektor: How did this script end up being your feature debut?

Santiago Arriaga: I was helping my mom clean the house. She had a box full of papers of everything that my father wrote. She was like, “I need you to help me with this. It’s taking up a lot of space.” So I opened the box and I found this script written on a typewriter. I was like, “Oh, wow, I thought this was lost.” When reading it, we found that the story connected to who we are. It’s a story about brothers that happens in a place that we have gone to since we were children, which is a northern state of Mexico, Coahuila, bordering the United States. So it’s a place close to our hearts.

The characters mainly know Coahuila through traumatic memories. How did your relationship with the region change through making the film?

Mariana Arriaga: Our father has been going there since he was 20-something. And then [after] we were born, our parents took us to many places in Mexico, but especially we would go back to Coahuila.

SA: It’s funny because where we shot the film, it’s a place [where] we are usually by ourselves. It’s a desert! Then suddenly, we had 100 people there. We were like, “This is weird.” It’s like having people in your house.

MA: But it’s such a special place for us. The story, originally when it was written in the ’90s, took place there so we wanted to keep it very loyal to the original script. We had built a deeper connection to that space by the time we shot there last year. Being there with family but also with our collaborators was pleasant.

I think, in a way, we’re very connected to these teenage spirits.

You’ve got this great trio of performances, and these characters bond while processing complicated stuff from every angle. What was the process of bringing what was on the page to your cast?

SA: These young actors are really connected to their emotions; each of them has an understanding of the script that I think was perfect. Working with young actors was [initially] one of our first concerns, and Theo [Goldin], Federica [Garcia], and Máximo [Hollander] taught us a lot on how to try things, relax, and cover different approaches to the story.

MA: I think our initial fear was that them being so young could go wrong. But very soon in the process, we started having rehearsals with them, and we talked about the characters, emotions, being on a movie set—for Federica and Theo, it was their first movie. He was 12 years old, she was 19. But they seemed very professional, very natural, very disciplined. Federica, for example, her character has a huge arc, so she used resources like changing the smell of her perfume for one part of the movie to another one. She invented whatever she could to achieve certain things for the character.

What was casting these unknown actors like?

SA: We did an open casting with over 600 [actors]. But it’s a funny thing: Theo is the brother of a friend of ours, Máximo and I became friends at an Ariel Awards ceremony in Mexico, and Federica is the daughter of a close friend of the family and we’ve known her since she was a little girl. 

MA: In the case of the character Paula: when she was some years younger—we’d been talking about the story for a while—our father told us, “You need to take a look at Federica seriously, because she’s got magnetism. She knows how to do this.” Even though we opened that huge casting, we had a hunch—we thought it was them. Of course we considered others, but we followed our instincts.

The characters are unobserved by adults for pretty much the whole movie, and you are adults directing these young, inexperienced actors. What was that process like?

MA: We feel their age! I don’t feel I’m an adult directing them—

SA: I feel [like] I’m fourteen!

MA: I think, in a way, we’re very connected to these teenage spirits, let’s say. We also went through this teenage stage of life not so long ago, where we responded to our emotions rather than to a rational side. So that’s what we wanted to keep in the film. Shooting it, we wanted to put these characters under a cloud, where they’re not able to see. They just follow what’s visceral. And suddenly these clouds start to let in the open sky.

During the climactic confrontation between the teens and Lucio, were there emotions or feelings you specifically wanted to evoke through the characters? How much trust was there in your actors to depict these really complicated emotions?

MA: A lot of trust, fully trusting them. As Santiago was saying, the three young [actors] are in connection with their emotions; they had a lot to bring into their own characters through their own experiences, their own way of conceiving of life. You can talk whatever you want to talk, but in the moment, you just need to leave them to do whatever they can do. They did amazing things, each of them. 

That final part, it’s like a mixture of emotions. All of the characters still cannot decide. They’re trying to get somewhere but don’t know how to get there. We never judge our characters; if we did, it would be a big mess.

SA: We have to follow them and be impulsive with them.