“The Endless Trench,” Spain’s submission to the Best International Feature category of the 2021 Academy Awards, features standout performances from its two leads who spend nearly all of the film’s 148-minute runtime on screen together.

A story of confinement and fear, “The Endless Trench” follows Spanish Academy Goya Award-winner Antonio de la Torre’s Higino as he escapes from Francoist soldiers at the onset of the Spanish Civil War. After spending hours hiding in a well with fresh floating corpses, Higinio makes his way home under the cover of darkness, unaware that he will spend the next three decades of its life hiding under floorboards and inside walls for fear of political repercussions due to his politics.

Higinio’s wife Rosa – played by Belen Cuesta whose performance earned her a Goya Award for Best Actress – must suffer through the decades along with her husband while living a double life outside their four walls where the slightest slip could mean imprisonment or even death for them both.

A Netflix Original outside of Spain and France, the film’s presence on a streaming platform has made it easily accessible and surprisingly relatable to audiences around the world who are themselves experiencing confinement resulting from the COVID-19 outbreak.

De la Torre and Cuesta spoke with Variety about the film’s universal themes, emotional and physical changes needed to play an aging couple, and the once in a lifetime opportunity a film like this presents to its actors.

What should viewers know, if anything, about the Spanish Civil War before seeing this film?

De la Torre: Even if the audience doesn’t know many details about the Spanish Civil War, I think that right now is a very polarized time in the world, and people can relate to the conflict between Gonzalo, a Franco supporter who torments our characters, and Higinio, a leftist whose political ideals get him in trouble. They see each other as enemies, as the other, and I think audiences everywhere understand that dynamic.

With most of us spending all our time at home over the past year, do you think that audiences have found something relatable, in a small way, to the film’s themes of confinement, boredom and monotony?

De la Torre: COVID-19 has probably been the most important global issue of our lifetime, but while other generations were compelled to go to war, we are just compelled to stay at home. When we were in the worst part of lockdown in Spain, we heard these questions a lot. People would always ask me about surviving lockdown as if I were now an expert! But at some point during this COVID period, I did begin to realize that maybe I could survive like this, I had my doubts while making the film, and how amazing the human capability for survival is.

Higinio might be the film’s main protagonist, but Rosa quickly becomes its hero.

Cuesta: I agree absolutely, and while our film doesn’t tell one true story, it borrows from real testimonies of survivors who lived events which inspired the narrative around our characters. When you read the stories of the real women who had to lie for so many years, to work, to survive and feed their children and their husbands, it’s fascinating. I think that maybe our film can help people recognize these women, because they were absolutely heroes.

This film was shot in two parts? Can you talk about why, and what you did with the time off?

De la Torre: We shot the film mostly chronologically, and the first shoot was four or five weeks long. When we stopped, I used the time to gain almost 35 pounds because Higinio would have gained weight stuck at home. We also studied in our downtime, watching videos of older couples walking together, talking to one another.

Cuesta: While waiting for Antonio to put on the weight I was working with coaches on establishing how Rosa would move and walk as an older woman. Rosa didn’t put on any weight because she was still going out and being active, but narratively it was important for Higinio’s physical change to represent his inability to leave the house.

The two of you are in nearly every scene of this film. How did you prepare together for such demanding roles?

Cuesta: One mind-blowing thing about Antonio is his very thorough attention to detail. I think the care he takes with details is what makes him such a great actor. We had more time than normal to prepare before shooting and Antonio and I helped touch up the script a bit. The directors are from the Basque Country but Antonio and I are from the south so we have a better idea of how people in Andalusia would speak and act during that time.

De la Torre: Belen and I were always together on set, especially towards the end where we were spending five-and-a-half hours in makeup. We tried to understand that when the years are passing by some things are lost, not only physically but emotionally. I think Belen did such a wonderful job. I’m a bit older than her and I remember telling her it was a once in a lifetime opportunity to get a role like this, and she absolutely took advantage of it.

“The Endless Trench” was directed by the award-winning Basque trio of Aitor Arregi, Jon Garaño and Jose Mari Goenaga (“Giant,” “Flowers”). What was it like working for three directors simultaneously?

Cuesta: I’m actually used to multiple directors having worked with Los Javis (“Paquita Salas,” “La llamada”). They say two heads are better than one, so three must be better still! That was definitely the case with this film. The directors clearly shared the same vision for “The Endless Trench,” so it was always with whoever was on set.

De la Torre: I never had the feeling of multiple voices telling us what to do. I love improvisation and reacting on set, and it was great working with directors that gave us the creative freedom to improvise. Also, they’ve worked together for 20 years so they would get into tiny arguments on set sometimes and they were like an old, long-married couple, which was perfect inspiration!