John R. Cash (Joaquin Phoenix) was a hard-drinking, drug-abusing, soul-searching, black-wearing, June-Carter-loving man. Yet for all his swagger and rage, he was persistently vulnerable, eager to impress the woman whom he heard sing on the radio when both were children, and desperate to please his hard-ass father Ray (Robert Patrick). A savvy songwriter and distinctive performer, Cash invented his own art even as he tried to fit in with Sun Records label mates Jerry Lee Lewis (Waylon Malloy Payne) and Elvis Presley (Tyler Hilton). He was the Man in Black, he missed his dead brother and he dedicated himself to June.

Or so it would seem in James Mangold's much-anticipated Walk the Line, a biopic that predictably showcases high and low points, and draws direct lines between tragedies and emotional fallouts. The problem with biopics is that they need beginnings and endings, and this one wrestles the man's unfigurable contradictions and passions into a typical, palatable shape. The movie opens on Cash, haunted by the trauma of his brother's death, and closes on a high note, an epigraph adding that Cash had 35 more years to endure before he and June (Reese Witherspoon) died within four months of one another.

The film's focus on the volatile relationship between Cash and the generous, God-fearing, self-judging June paints a good-woman-behind-a-great-man portrait, such that June appears only as he knows her, without a life of her own (the script is drawn from Cash's two autobiographies). Just so, the relationship dates back to his childhood, when he listens to 10-year-old June on the radio and angers his father. With the Good June-Bad Daddy nexus in place, the film traces little J.R.'s yearnings in the most rudimentary way: At 12, he picks cotton on his father's Dyess, Ark., farm in 1944, learns hymns out of his mother's book, and dotes on his older brother Jack (Lucas Till).

The trauma-that-becomes-life-crushing-guilt comes when J.R. leaves Jack to work a bandsaw one Saturday afternoon (even after seeing the machine is faulty), then holds his hand in the hospital while Jack dies, bloody, pasty white and eternally "good." Ray blames J.R. ("You're nothin'!") and the boy pursues music, in a roundabout way, buying his first guitar while serving in the Air Force in Germany in the early 1950s. He sees a newsreel about Folsom Prison, feels a kinship with the inmates, and writes "Folsom Prison Blues," the song with the dicey lyric ("I shot a man in Reno, just to watch him die") that convinces Sam Phillips (Dallas Roberts) to sign him. (His first hit, however, is "Cry, Cry, Cry," in keeping with the pop-country mode so popular at the time.)

Walk the Line's mythologizing of the Man in Black is premised on existing stories, its episodic structure making use of well-known events and figures. Cash's marriage to Vivian (Ginnifer Goodwin) is plagued by his expanding sense of guilt for everything that she wants and he can't deliver (she gets the big house, but not enough of his time) and his increasing dependency on amphetamines and alcohol. The film also makes his desire for June a driving force. They meet on a Sun Records tour when both are married, the attraction instant and mutual, even though (or because), as she notes, he's in need of mothering. She rejects this role, even as he drunkenly suggests that what she's really trying to fight off is their sexual connection.

While Cash is surely a fascinating character—effectively dark and tortured in Phoenix's performance—June's role is almost painfully intriguing, as she's pushed to the side in most moments, supporting her man in all circumstances. She literally pulls him out of a lake during one wrenching Thanksgiving upheaval and sits in the back of the room during his famous live Folsom Prison recording in 1968, the camera changing focus from his ravaged face onstage and beloved by his inmate audience, to hers, composed and stalwart, utterly dedicated.

Her own anguish has to do with her faith and her insistence that Cash follow the Lord en route to finding some unstable peace with her. They try to make sense of their mutual attraction, keep proper distance, and parent their respective children from afar. Cut to a moment of seeming freedom and nostalgia, as June teaches Johnny to cast his fishing rod: They come close, pull apart, and go back on the road, where Johnny's waywardness continues to wear her down.

June's devotion makes all the difference, in the sense of their glorious duets (several thrilling moments, with Witherspoon and Phoenix singing in earnest, haloed two-shots) and repeated exchanges wherein June instructs Johnny on his errors. Here, as in the video for "Hurt" (directed by one of the movie's executive producers, Mark Romanek), June's gaze makes Johnny seem brilliant and gifted. It's a familiar story, and it makes you think that the true innovation might lie in her.

Walk the LineDirected by James Mangold A 20th Century Fox release Opens Friday at area theaters