The Man in Black may be gone, but his shadow and his sound live on in “Walk the Line,” the thoroughly entertaining new Johnny Cash film biography.

Joaquin Phoenix gives a soulful and musically dexterous performance as Cash. And the always-winning Reese Witherspoon brings bubbly charm and earthy warmth to June Carter, the great love of Cash’s life.

It tracks Cash from his humble and troubled, tragic childhood to his service in the military and his struggles afterward to land in the music business.

We follow him into Sun Records and into history, as Cash became part of a rockabilly line-up that included Elvis Presley and Jerry Lee Lewis.

We see him struggle with a bad marriage and a drug habit. And we see the lifeline that June Carter came to represent, over the long years he pursued her (both were married) and she kept him at arm’s length, a man who couldn’t “walk the line.”

“Walk the Line” invites, begs, comparisons to last year’s award-winning musical biopic, “Ray.” They’re both about beloved musical icons of virtually identical status. They both follow lives of hard knocks, hard love won and lost, and battles with addiction.

But “Line” uses the biography as backdrop. What it really is, is a love story. It’s about Cash, his rise and fall, and the woman he loved and pursued and courted, the woman he led, as her song puts it, into the “Ring of Fire.”

Johnny Cash (Joaquin Phoenix) and June Carter (Reese Witherspoon) perform onstage together in Walk

Director James Mangold’s film is framed within one of the highlights of Cash’s life, his 1968 concert at Folsom Prison. Cash relives his personal journey as he waits to give the comeback performance that would make him a legend.

The script, co-written by Mangold and Gill Dennis, is faithful to that legend. It’s based on Cash’s autobiography, so naturally his first wife (Ginnifer Goodwin) is played as a shrew. But they also have fun with Cash’s reputation. When Johnny, at the end of the long slide that terminated with a drug bust, stalks into his record company to announce his prison concert, to be recorded live for an album, a record exec gripes about his wardrobe.

“What’s with the black? You look like you’re goin’ to a funeral.”

“Maybe I am,” Phoenix-as-Cash growls.

Phoenix, an actor long on sensitivity, plays the script’s central thesis to the limit, that Cash lived his whole life with survivor’s guilt. It’s a bit trite, and isn’t nearly the obstacle that “Ray” wore as a badge of honor. But Phoenix makes it believable.

Witherspoon doesn’t so much transform herself into the mountain girl/country royalty that June Carter was. She grafts Carter onto her own vibrant personality.

And with Witherspoon in the role, it’s easy to believe a bereft Johnny would hike miles through Nashville in the pouring rain, long after reaching stardom, just to have her reject him again.

Robert Patrick plays his bitter, disapproving dad; Shelby Lynne is a virtual non-presence as Cash’s long-suffering mother. A couple of good scenes don’t become all they could due to weak casting in some supporting roles – Sun Records’ Sam Phillips was a huge personality, something Dallas Roberts doesn’t get across here.

But that’s quibbling. “Walk the Line” is a spirited and winning reminder of the man before he became the legend, of the giant shadow he cast, and of the remarkable woman who cast her shadow over him.