Neither Lazarus nor Rae is in a good place as Black Snake Moan begins.

Lazarus (Samuel L. Jackson), a former bluesman turned farmer, has just lost his wife to his brother, Deke (Leonard L. Thomas), whom he nearly kills, Cain-like, in the local bar where Lazarus used to perform. Rae (Christina Ricci), on the other hand, is lying unconscious in the road in front of Lazarus's farmhouse, the victim of sex, drugs and physical abuse, all of which are very clearly depicted for us in this very R-rated movie.

Just where they'll go from there is anybody's guess -- no, it's actually the guess of Craig Brewer, the writer-director who rocketed to fame two years ago on the success of Hustle & Flow, which won an Oscar for the song "It's Hard Out Here for a Pimp."

And Brewer's course is clear, even if the motivations of his characters aren't. Lazarus picks up Rae and carries her into his farmhouse, where he decides -- for reasons that seem to have something to do with the Bible -- to nurse her back to health.

But that's going to be a bigger job than Lazarus realizes. Because -- unlike the audience -- Laz, as his friends call him, doesn't know anything about Rae. We don't know a lot, but Brewer's already revealed this much: Minutes after sending her first steady beau of her life (Justin Timberlake) off to National Guard duty, Rae reverted to her former life as town slut -- drinking, doing drugs and getting to know anyone she can in, shall we say, the biblical sense.

So it isn't long before Lazarus finds Rae wandering about his house and fields in a state altered by both the drugs she's been taking and the fever she hasn't been treating. So Lazarus does the only thing he can think of to help her: he chains her to his radiator.

At this point, watching Black Snake Moan becomes a bit uncomfortable, to say the least, not because we think Lazarus is out to do anything wrong, but because we know what the people of the small Southern town in which they live -- including her boyfriend, whose tour gets cut short -- would think he was out to do.

And so BSM morphs from troubled personal film into psychological thriller. What are these people doing and why? And what will their neighbors do when they find out?

But to focus too much on the storyline is to overlook the real successes of Black Snake Moan.

First, there are the performances by Ricci and Jackson. Both are performers who are hard not to watch.

As the somewhat consumptive -- even anorexic at times -- Rebel-flag-wearing Rae, Ricci accomplishes the near impossible: She gives trailer trash a bad name. (See how fast she loses what little shorts she has for the duration of the film.)

But Jackson is even more intriguing here because of Lazarus's past: his blues past, that is. Lazarus was a popular local performer, and he breaks his guitar out on more than one occasion. Fortunately for us, Jackson, who reportedly learned to play guitar for the film, is up to the task, as he demonstrates on a number of songs, including the traditional "Stackolee," "Catfish Blues" and the title track.

Add to them nearly two dozen songs by other performers such as Big Jack Johnson, R.L. Burnside and the Tate Country Singers (doing a great version of "Jesus on the Mainline") -- plus an appearance (actually two) via black-and-white archival film clips of the late great Son House talking about the blues -- and you have a film that may not rock, but it surely sings.

OK, it's not always easy to follow Lazarus's logic -- why he suddenly decides to take in Rae, why he suddenly decides to stop trying to control her life, why he suddenly picks up his guitar and returns to public performing and why he decides Rae should accompany him (other than to let the audience see Ricci do some dirty dancing). But then what do you expect from the black-and-blues version of My Fair Lady?

Rational it's not. Affecting and effective it is.