As period pieces go, BPM (Beats Per Minute), the story of AIDS activists in Paris in the early 1990s, is light on the trimmings. The jeans may be cut differently, and bomber jackets abound, but French-Moroccan director Robin Campillo avoids the trap so many filmmakers, emboldened by healthy budgets or sheer nostalgia, fall into. Remember how Tina Fey joked that the original title of American Hustle was “Explosion at the Wig Factory”? The members of ACT UP Paris featured in BPM don’t look as though they’ve just bought their entire wardrobe off the rack. The evocation of an era is subdued; it could almost be now.

What makes the distance between that time and this one so stark is the way in which outraged words are directly linked to action. There’s a certain kind of contemporary activism that, as American writer Rebecca Solnit has put it, “sometimes seems to make the left the true heirs of the Puritans. Puritanical in that the point becomes the demonstration of one’s own virtue rather than the realisation of results.” In BPM, results are a matter of life or death, and there’s nothing puritanical about its principal characters: young gay men, women and haemophiliacs who gather once a week to plan direct actions against the state or pharmaceutical companies. There’s a directness to the way they dance and fuck and argue, born of the knowledge that time is not unlimited.

Founded in New York in 1987 to fight bureaucratic indifference to the AIDS epidemic, ACT UP emerged in Paris in 1989 (and in Australia the following year, with members staging protests outside the American consulate and even abseiling onto the floor of federal parliament). Young activists brandished placards at “die-ins” with the words “silence = death”. In an era when television was paramount, the group’s actions were designed to make the nightly news.

Campillo joined ACT UP Paris in 1992. A graduate of the prestigious film school now known as La Fémis, he would emerge at the end of that decade as an editor and screenwriter, working frequently with his classmate Laurent Cantet on films such as Time Out (2001) and the Palme d’Or–winning The Class (2008). But in 1992 he was a young man increasingly disillusioned with filmmaking in the face of the AIDS crisis. “I thought cinema was pointless,” he says. Campillo lost friends and lovers to the pandemic. One of them – his first boyfriend, Arnaud – is a ghostly presence in the film, which is threaded with autobiographical details as well as characters and actions loosely inspired by historical ones.

In a monologue midway through BPM, Nathan (Arnaud Valois), a new member of ACT UP and one of the few who isn’t HIV-positive, shares a story explicitly taken from Campillo’s own life. Nathan tells his “poz” lover, Sean (Nahuel Pérez Biscayart, a dead ringer for Peter Lorre, only sexy), about his first boyfriend, Arnaud. The two stopped sleeping together as soon as the epidemic hit, he says, only to reunite years later. Nathan notices that Arnaud is having trouble walking, and subsequently learns that he’s been admitted to hospital. Although Campillo provided plenty of room for improvisation during the shoot, this scene was ironclad. “I did it the first day and I was changing some words,” Valois recalls. “Robin said, ‘We’re going to do it tomorrow, and you [should] relearn your lines.’”

Campillo wrote the screenplay with Philippe Mangeot, a fellow activist whose father worked for the manufacturers of AZT, the first publicly available HIV/AIDS drug. (Mangeot would absent himself whenever ACT UP staged an action against his father’s company, Burroughs Wellcome, on which the film’s big pharma bogeyman, Melton Pharm, is modelled.) The two worked on the script for the better part of a decade, relying mostly on memory. For Campillo, the writing became a process of tabulation. “I just wanted to understand. Not the meaning, because that’s a lost cause. I just wanted to put things in perspective. It was like trying to structure your own life.”

What he’s come up with is a study in contrasts. The film glides between three worlds: the lecture hall where the group’s weekly meetings are held, the public actions staged on the streets of Paris or at the offices of pharmaceutical companies, and the clubs where the activists go to dance the night away after they’ve been released from police custody.

Though BPM is a true ensemble piece, it also zeroes in, eventually, on three characters. There’s Nathan, sweet and shy and a tall drink of water, whose first appearance elicits wolf-whistles from his fellow activists. There’s Thibault (Antoine Reinartz), ACT UP’s president – a head prefect–type. And sitting in the bleachers lobbing grenades is the more radical Sean, with whom Thibault frequently clashes. As befits the amphitheatre in which meetings are held, it’s about performance.

“For many years I felt like I was an imposter,” says Campillo, “because I was feeling the fact that I was playing [a role], that it was a theatrical thing to live your life. This generated the characters, because Sean is someone who has been burning himself up in life, in the struggle against AIDS. When I was younger I was jealous of this kind of guy, because I was feeling remote from reality. I was more like Nathan, over-protecting myself from the disease but also from life, from everything. I was looking at reality [from] behind the glass.”

Valois hadn’t acted in a film for six years and was working as a massage therapist when he got the call from Campillo’s casting directors, while the Argentinian Biscayart only learnt French, remarkably, six years ago. Neither knew much about ACT UP, but swotted by reading a history of the movement by Didier Lestrade, the co-founder of ACT UP Paris (and a clear model for the character of Thibault). Biscayart watched documentaries on Cleews Vellay, the firebrand member of ACT UP Paris who was president from 1992 until his death in 1994 at the age of 30.

In auditions Valois and Biscayart ran through the film’s centrepiece sex scene, in which Nathan and Sean talk about the disease and past lovers, the two inextricable. “At the beginning it was about creating an intimacy,” says Valois. “We had two casting sessions together and we clicked by the second one. By touching. We were bare-chested, and we could feel that there was something happening. You’re conditioning yourself to be in a couple with someone for two-and-a-half months. It’s about spending time with someone, talking about anything – personal life, hobbies, dreams, nightmares – to create something that’s maybe artificial but that can appear real.”

Over three days of group rehearsals, Mangeot talked to the entire cast about his time in ACT UP. “Philippe gave us a lecture on that time in [the] first person, using present tense, and everybody was completely moved,” says Biscayart. “He talked about very big political issues and also about very small details, like what it was like to bend a dead body when you had to dress it up. All those details that inhabit your body in a very specific way. It’s hard to imagine how those guys and girls lived back then, burying friends, lovers. I can’t even get close to that.”

Though it brought hard-nosed journalists (not to mention jury chair Pedro Almodóvar) to tears at Cannes, where it won the Grand Prix last year, the film is clear-eyed rather than sentimental. Sean and Nathan’s burgeoning relationship doesn’t really emerge until midway through, and BPM isn’t afraid to present it as one of convenience that’s also deeply felt. “We tend to see love as this pure thing,” says Biscayart. “Whereas of course everything is also a matter of necessity and convenience. In this case, maybe if the sickness wasn’t there the love story would just have been a little fling.” Campillo’s previous film, Eastern Boys (2013), likewise explored a relationship neither transactional nor wholly equal, one in which sex speaks volumes.

“Personally,” the director says, “I love sex. I love filming sex. I have no problem with that, and I think it’s very relevant.” Like Nathan, Campillo never visited Arnaud, his first boyfriend, in hospital, and still misses him. “I don’t miss him because of our discussions. I miss him because I loved to have sex with him. I’m so sorry we can’t have sex anymore. That’s the main thing. It’s not a small thing. It’s a political thing. When you miss someone you miss his skin, his smell. I don’t make sex scenes to shock the bourgeoisie. I do it because I like it. It’s connected to a belief in sex as something which is very crucial.”

BPM opens with members of the group huddled in the wings of a conference hall, whistles in mouths, about to storm a stage. This “zap”, against the government agency set up to deal with the crisis, is intercut with ACT UP’s subsequent meeting, in which the participants discuss how the action played out. Sophie (Adèle Haenel) is convinced they went too far by restraining the speaker and splattering him with fake blood. Sean is having none of it. The government agency’s public health campaigns are so abstract you’d hardly know the disease was sexually transmitted, he says, and the entire organisation is nothing but a cover: a way for the government to shift accountability.

Campillo based the sequence on a real-life action that targeted those responsible for the transfusion scandal, in which infected blood was given to haemophiliacs. But the action and the internal debate it provoked also recall the storming of New York’s St Patrick’s Cathedral in 1989. In an oral history of ACT UP New York, the group’s founder, Larry Kramer, remembered the response. “Everybody was terrified after it, because it had been in the paper and every editorial page in town had dumped on us. People were scared, and I remember saying, ‘Are you crazy? Are you crazy? They’re afraid of us now! That’s the best thing that could have happened to us!’”

Whenever Sean and Thibault collide, the film becomes as much a study in activist tactics as it is a romance. “For Thibault, the existence of Sean is very healthy for the group,” says Biscayart. “Because he was the one who at some points was pushing harder for things to advance.” The importance of negotiation and protest rather than one or the other was a lesson Kramer brought to ACT UP from his time in the movie business, working in London in the 1960s (where he wrote Ken Russell’s Women in Love, the one with Oliver Reed and Alan Bates wrestling in the nude).

According to Kramer, that’s how every successful company, of any kind, really works. “You’ve got a shit executive, who fires everybody, or cuts everybody’s budget. And you’ve got a saint executive, who keeps everybody happy. And don’t think they don’t talk to each other, at the end of the day, to compare notes.” In ACT UP, “the bad cops were all the kids on the floor, and the good cops were all the people inside doing the negotiating”.

For the auditorium scenes, Campillo and his cinematographer, Jeanne Lapoirie, shot scenes from start to finish with multiple cameras fitted with zoom lenses. The director felt liberated from what he calls the “frame-control fetish” that characterised his debut, 2004’s They Came Back, and BPM is altogether looser, almost documentary-like – though its transitions are anything but.

Campillo co-edited the film, and BPM is defined by the fluidity with which it moves from one space to the next, what he calls “wormholes between dimensions”. Dust motes in a club dissolve into plasma; Sean and Nathan go from dance floor to bed without a definitive cut; the ghosts of former lovers appear in the middle of a sex scene. “I love the idea that cinema is very impure. You can have very raw, realistic material, but it’s generated in a machine which is more complex. If you put mice in a laboratory, mice are very realistic. But the structure they are living in is absolutely not.” Campillo likens the film to a roman-fleuve, a “river novel”, one that flows through histories. In its most haunting sequence he conjures an action ACT UP planned but never executed, dyeing the Seine blood red.

The importance of physical presence, appearing in flesh and blood to make an “invisible war” visible, is central to BPM. “This is what a person with AIDS looks like!” shouts Sean, storming Melton Pharm’s office to protest its failure to release lab results. The tension between him and Thibault springs, above all, from the degree to which each is embodying the struggle – from an imbalance in urgency. Thibault might be HIV-positive, but he’s not dying. One woozy slow-motion shot even sees him watering his garden, investing in a future that Sean will never see. “When you’re talking about a disease, it’s your body which is at stake,” says the director. “So it becomes politically something that is electrifying, burning. And it creates a relationship to time that is very different.”

The film was shot in sequence to allow Biscayart to lose weight as the production went on. “It doesn’t really show in the film,” he says, “but at the time my friends were so afraid.” Early on Sean leads a group of pompom-wielding cheerleaders at the annual pride march. But as he declines, his sense of theatricality disappears. At the pride march the following year, he’s barely there, a man with a thousand-yard stare.

“The emotion that you see in the character comes from the fact that his body no longer has a place in society,” says Biscayart. The actor worked with Campillo on peeling away Sean’s sense of play, leaving a body that is less flamboyant but, crucially, just as inhabited. “We don’t see the physical movement and that intensity, but the body is absolutely vibrating and shaking with the idea that it’s no longer going to inhabit the world.”

The closest Sean can get to an action is watching his friends on television from his hospital bed, and the power of the film’s final act is the sense of loneliness it conveys. The withdrawal from a community that was all-consuming, what Campillo has described as the “tunnel of solitude”. But BPM’s final scene bridges his isolation, with Sean’s friends and lovers taking him with them on an action. As the members of ACT UP shout and point at a startled gathering of insurance reps, the lights switch to stroboscopic, as if they’re back in the club. Bodies flailing in darkness, bodies merged into one. Campillo is nostalgic for clubs, which remind him of cinemas. “These dark places with light phenomena on the screen or around us, where we are all alone together.”

BPM is screening at the Alliance Française French Film Festival and then in limited national release.

Harry Windsor

Harry Windsor is a critic for The Hollywood Reporter and the former editor of Inside Film.