"LOCKDOWN" doesn't tell you much about prison life that the movies (or possibly a stretch in the joint) haven't told you already. But it does take this occasion to confirm every horrible detail, from rape to murder with sharpened shivs. You were wondering, weren't you?

If there's anything to be learned from this ruthless potboiler, it's that Richard T. Jones, who has appeared in "The Wood" and is Bruce Van Exel in the television series "Judging Amy," is a hugely appealing presence.

In Preston A. Whitmore II's screenplay, he's Avery, a competitive swimmer who makes the mistake of riding with his old homeboys Dre (De'Aundre Bonds) and Cashmere (Gabriel Casseus) and straight into prison.

Falsely accused of murder -- we see who the real killers are -- the three are arrested and convicted. Suddenly three friends, once there for each other, have to fend for themselves in the big house, where the usual tattooed, muscular and extremely surly prisoners are waiting for them, conveniently arranged into ethnic gangs for easy reference.

Avery tries to steer clear of trouble and gets help from a kindhearted older cellmate (Clifton Powell). Cashmere falls in with the black gang, run by a hustler named Clean Up (Master P). And poor Dre gets the worst of it, thanks to the psychotic redneck he bunks with. I'll spare you the details.

Whitmore and director John Luessenhop won't get awards for originality, but they can expect dubious acclaim for their attention to the nastiest elements of prison life. The performances are strong. In addition to Jones, Bonds is particularly touching as he faces a horrible, no-way-out future. But no matter how convincing they are, they can't break out of the dramatic prison the rather hackneyed screenplay has built around them.

LOCKDOWN (R, 100 minutes) -- Contains brutal violence including sexual assaults, pervasive obscenity and graphic drug use. No song and dance numbers. Area theaters.

Master P plays an incarcerated hustler named Clean Up in "Lockdown," a story of three friends who are wrongly convicted of murder and end up fighting for survival in the big house.