The New York-based writer-director Ira Sachs has a gift for putting romance, gay and straight, under a microscope. In his earlier independent dramas, like Forty Shades of Blue, Keep the Lights On and Love Is Strange, he examines all the things that can test a long-term relationship, from infidelity and addiction to issues around money and real estate. But while Sachs' storytelling is rich in emotional honesty, there can also be a muted quality to his work, as if he were studying his characters rather than plunging us right in alongside them.

There's nothing muted, though, about his tempestuous and thrillingly messy new drama, Passages, mainly because its protagonist is the single most dynamic, mesmerizing and frankly infuriating character you're likely to encounter in one of Sachs' movies. He's a Paris-based film director named Tomas, and he's played by the brilliant German actor Franz Rogowski, whom you may have seen — though never like this — in movies like Transit and Great Freedom. From the moment we first see him berating his cast and crew on the set of his latest picture, Tomas is clearly impossible: a raging narcissist who's used to getting what he wants, and seems to change his mind about what he wants every five minutes.

The people around Tomas know this all too well and take his misbehavior in stride, none more patiently than his sensitive-souled husband, Martin, played by a wonderful Ben Whishaw. When Tomas has a fling with a young woman named Agathe, played by Adèle Exarchopoulos, Martin is willing to look past it; this clearly isn't the first time Tomas has slept with someone else. But Agathe stirs something in Tomas, and their fling soon becomes a full-blown affair.

Passages is a torrid whirlwind of a story, where time moves swiftly and feelings can shift in an instant. Before long, Tomas and Martin have called it quits, and Tomas has moved in with Agathe. But ending a marriage of several years is rarely clean or easy, and Sachs and his longtime co-writer, Mauricio Zacharias, chart the emotional aftermath in all its confusion and resentment. Martin wants to sell the little cottage they own in the French countryside, but Tomas wants to keep it. Even after he's moved out, Tomas keeps bursting in on their old apartment unannounced, despite Martin's protests that he doesn't want to see him anymore.

Tomas feels jealousy and regret when Martin starts dating another man, which is hard on Agathe, especially when she finds out she's pregnant. Agathe is the most thinly written of the three central characters, but here, as in her star-making performance in Blue Is the Warmest Color, Exarchopoulos is entirely convincing as a young woman trying to figure things out.

Tomas is clearly bad news, a destructive force unto himself and in the lives of those around him. It's hard to look at him and not see echoes of Rainer Werner Fassbinder, the great German filmmaker whose personal relationships were as notoriously fraught as his movies.

But as maddening as Tomas is, he is also, in Rogowski's performance, a powerfully alluring figure whose desires can't be pinned down. Tomas is thrilled and unsettled by the feelings Agathe unlocks within him, but he still yearns for his husband after they separate. And Martin, played with moving restraint by Whishaw, can't help being drawn back to Tomas, against his better judgment.

At one point, Tomas and Martin have sex, in a feverish scene that Sachs and his cinematographer, Josée Deshaies, film in an unblinking single shot. It's one of a few sex scenes here whose matter-of-fact candor earned the movie an NC-17 rating from the Motion Picture Association last month. Rather than accept this outcome, the movie's distributor, MUBI, opted to release the film unrated and publicly criticized the ratings board for marginalizing honest depictions of sexuality. It's hard not to agree. It's the intimacy of Passages that makes Sachs' characters so compelling and so insistently alive.