The film begins with the stuff of nightmares: a dark bull breathing heavily and looking directly at the viewer while evening enshrouds its massive bluish-black bulk. Seemingly suspicious, he then skittishly moves a bit here and there in what looks like a clearing in a forest. Soon, another bull is shown, its face, horns, and heaving mythic and monstrous.

This prologue belongs to “Afternoons of Solitude,” and it’s not a horror film, strictly speaking. It’s a documentary by a Spaniard, Albert Serra, and its subject is bullfighting. A sport for some, a spectacle for others, and a moral travesty for many, the tradition of killing bulls in a ringed amphitheater becomes, in the hands of the director, an approximation of a slasher movie, complete with blood and guts, heart-stopping scares, and occasional ominous music.

The film’s unflinching look at the gore rooted in Spanish bullfighting and the death-defying antics of its performers begets the question of whether Mr. Serra intended to condemn the ritual, which can be traced to prehistoric times. Yet the director’s opinion proves slippery, as the documentary unflinchingly focuses on a particular matador, his entourage, and his adversaries in the ring — without any obvious moralizing from commentators. 

Quoting Hemingway, who wrote two nonfiction books on the subject, may help here. In the first, 1932’s “Death in the Afternoon,” the author’s viewpoint is summed up in the following sentence, which may double as a defense of “immoral” cinema, particularly horror and violent films: “I know only that what is moral is what you feel good after and what is immoral is what you feel bad after and judged by these standards, which I do not defend, the bullfight is very normal to me because I feel very fine while it is going on and have a feeling of life and death and mortality and immortality, and after it is over I feel very sad but also very fine.”

The film’s matador is a Peruvian bullfighter, Andrés Roca Rey, a handsome vicenarian. When we first see him, he is sweating profusely in a luxury van after a bout. It’s not until the next scene, within his hotel room, that we notice the blood on his sparkling outfit. It is not his, though he talks of a previous wound with his handlers, one of whom helps him to undress. 

Next we see him and his retinue heading to another arena in Spain. This pattern — footage within the transport vehicle, a hotel room before or after a fight, and the spectacle itself — will be repeated a few times, with no sidelines into the history of the sport or the matador’s backstory, though it becomes clear that he wishes to be respected by Spanish aficionados. 

The first bullfighting scene lasts about 20 minutes, with Mr. Serra ignoring the opening pageantry to show Andrés’s teammates as they slowly bleed the steer with piercings to its shoulders. This is a preamble to the final and iconic stage of the tradition, when Andrés twists and turns with his red cape as the bull sweeps past him — its horns mere inches away from the young man’s boyish body — until the final kill is performed.  

Mr. Serra and his cinematographer, Artur Tort, film the action primarily with medium shots, from Andrés’s torso up, making an already tense situation even more nerve-racking with the tight framing. Sometimes, these shots resemble abstract action painting, with their flashes of color, movement, light, and shadow as the bull rushes by. Red is the stand-out color, of course, and different shades of red beat a thrilling pulse throughout the film, such as the wine red of one of Andrés’s costumes, the pink of his stockings, the crimson or maroon of the painted wood around the grounds, and the alternately dull or bright scarlet of blood. 

Several near tragedies transpire, but none will be remembered more than the one that occurs at about the hour mark. Afterward, with Andrés in the van looking grateful to be alive, his colleagues praise his fighting style and immense courage. One of them calls him “superhuman” as he casually bites his nails. There is a sense that he is in shock, which could also be ascribed to the viewer. 

An extended scene of Andrés dressing for a fight with the help of his assistant demonstrates the almost comical contortions involved, while also depicting the matador’s religious piety and the superstitious preparations undertaken to ensure a safe return. The keynote in this scene and others is silence, such as the hush that overtakes the crowd just before the final thrust of the sword. Another central motif is isolation, with Andrés frequently alone in his thoughts despite having his crew or the crowd always nearby.

Mr. Serra achieves something rare with “Afternoons of Solitude”: a near total state of rapt attention for two hours while sidestepping potential glamorization through formal stillness and thematic purity. It’s as close to experiencing the bullfighter’s process before, during, and after the fight as one may wish to get. One may denounce bullfighting’s cruelty and look away in horror at times — I certainly did — but the documentary’s austere linking of bravery and barbarity confirms the tradition’s crude yet elegant poetry.