Joaquin Phoenix stars as Leonard, a troubled young man torn between two very different women, in the James Gray film Two Lovers. (Alliance Films)

Back in February, actor Joaquin Phoenix showed up on Letterman, ostensibly to plug his new film, Two Lovers. Instead, he gave one of the strangest performances of his career.

If Two Lovers really is Joaquin Phoenix’s farewell to the dramatic arts, it’s one powerful swan song.

Wearing dark glasses and a beard worthy of Larry Charles, the mumbling, gum-chewing Phoenix claimed with a straight face that he’d chucked acting and was going to become a hip-hop artist. The jury is still out on whether he was sincere or pulling an Andy Kaufman-sized put-on. (Casey Affleck has been shooting a documentary on Phoenix’s musical transformation, which suggests it could be the latter.) In any case, if Two Lovers really is Phoenix’s farewell to the dramatic arts, it’s one powerful swan song.

The film, directed by James Gray, is a dour, beautifully acted drama about infatuation. Phoenix plays Leonard Kraditor, a bipolar young man trying to get his life back on track after a devastating breakup with his fiancée that led him to make a suicide attempt. Now, Leonard is living with his Jewish parents in their Brooklyn apartment and doing deliveries for his father’s dry cleaning business. He’s lying low, taking his medication, but he’s far from recovered — in the opening scene, he plunges fully clothed into Sheepshead Bay, in what appears to be another effort to end his life.

Meanwhile, Leonard’s aging father, Reuben (Moni Moshonov), is in the midst of accepting a merger proposal from a fellow dry cleaner, Michael Cohen (Bob Ari). The shrewd but friendly Michael, an old-fashioned family businessman, is eager to bring the Cohen and Kraditor clans together as well. He has a single daughter, Sandra (Vinessa Shaw), who could be the perfect partner for Leonard, provided the boy doesn’t mess things up. Leonard and Sandra meet during a family get-together and, while sparks don’t exactly fly, they do hit it off. Sandra, intelligent and sensitive, draws out the shy, awkward Leonard, who reveals his tortured past. She’s a sea of tranquility (her favourite movie is The Sound of Music) and she offers the promise of stability that Leonard needs.

Then along comes the stunning, unstable Michelle (Gwyneth Paltrow). She’s a new neighbour in Leonard’s building and they meet in the hallway, where she claims she has fled during an argument with her father. Leonard invites her into his family’s apartment and is immediately smitten with her. He cultivates their acquaintance and before long he’s swept up into Michelle’s emotionally fraught world. She’s a legal secretary with a history of drug abuse, and she’s entangled in an affair with a married older man. Michelle needs a confidant and she leans on Leonard, not realizing he’s obsessed with her.

Michelle’s hot/cold relationship with the middle-aged Ronald (Elias Koteas) has Leonard swinging wildly between her and Sandra. He’s caught in a classic dilemma, an Adam faced with both an alluring Lilith and a trustworthy Eve. He tries to pretend indifference when Michelle talks of Ronald, claiming Sandra is his girlfriend, but it’s no use — he’s hopelessly besotted. Michelle’s apartment is across a courtyard from Leonard’s, and when they call out to each other from their windows in the dusk, there’s a frisson of classic tragic love — Leonard has become a starry-eyed Romeo in Brooklyn.

Michelle (Gwyneth Paltrow) involves Leonard (Joaquin Phoenix, right) in her affair with a married man (Elias Koteas). (Alliance Films)

The screenplay, by Gray and Richard Menello, is inspired by the Dostoevsky novella White Nights (mostly famously filmed in 1957 by Luchino Visconti). Menello and Gray relocate the story to present-day Brooklyn, but keep the Dostoevskian mood. The film unfolds in autumn and winter and its setting, the Brighton Beach area, feels overcast and oppressive. The Kraditors’ apartment is both cozy and musty, cluttered with ancient family photos and tchotchkes (Michelle says it smells of mothballs). Brighton Beach has a heavy, Old World air that Leonard only escapes in the blare of a nightclub with Michelle and her friends, or in a glittering midtown Manhattan, where he has an uncomfortable dinner with her and Ronald. Like Gray’s previous films, The Yards and We Own the Night (both of which starred Phoenix), Two Lovers is drenched in atmosphere.

In their last collaboration, the ultra-sombre cop drama We Own theNight, Phoenix’s performance was dampened by the heavy mood. This time, Gray has crafted a subtler film, and Phoenix responds with a richer portrayal. When we first meet the shambling, shlubby Leonard, he looks like a man uncomfortable with living, a guy who can’t even relax in his own bedroom. When he falls for Michelle, his giddy infatuation is both liberating and pathetic. There’s a core of naivete and vulnerability to Leonard, qualities that have been part of Phoenix’s arsenal going back to 1995’s To Die For.

Paltrow is equally compelling as Michelle, who is by turns welcoming, wounded and, in one chilling scene, beyond reach, her eyes like dull stones. Her pale blond beauty has a slightly worn quality here, a hint of brittle fragility. Michelle is just as damaged as Leonard, if not more so.

The supporting cast is faultless, from Shaw’s appealingly ordinary Sandra to Koteas’s casually superior Ronald. The most surprising character is Leonard’s mother, Ruth, played by the elegant Isabella Rossellini. Understandably vigilant in light of her son’s attempted suicide, Ruth comes across at first as a meddler, spying on Leonard and questioning him about his every move. It is only near the end of the film that we realize how much she loves and understands him.

Viewers looking for clues to Phoenix’s current hip-hop madness will find an odd foreshadowing early in the movie. Heading to the nightclub in a car with Michelle and her pals, Leonard reveals that he writes his own rap songs and then performs part of one; later, at the club, he also indulges in some old-school break dancing. But those were the only times in Two Lovers when I found myself thinking of Phoenix the celebrity and not the character he so brilliantly plays. Don’t quit your day job, Joaquin — you’re too good at it.

Two Lovers opens in Toronto and Vancouver on April 10.

Martin Morrow writes about the arts for CBCNews.ca.