"Charlotte Forten's Mission: Experiment in Freedom," tonight's two-hour Civil War docudrama on PBS' American Playhouse (9 on Channel 26 and Maryland Public Television stations), is the story of a privileged young black woman's trek across the Mason-Dixon line from Philadelphia to educate freed slaves in South Carolina.

Starring Melba Moore and Ned Beatty and brimming with dramatic promise, it is, to be sure, a noble experiment -- which quickly becomes an experiment in boredom.

Samm-Art Williams' disappointing teleplay, based on Charlotte Forten's real-life diary, has "educational" written all over it. "Excuse me, sir, we are dealing with human beings, not theoretical principles," one woman lectures the featured speaker in a lecture hall. "Land, boy!" says another while spilling dirt through his fingers. The characters seem to be prisoners in a series of meetings rather than participants in an unfolding story.

Director Barry Crane, making matters worse, frequently has the actors facing each other across a desk (or some other piece of major furniture) and telling us what they're going to do tomorrow or what they did yesterday or, most annoying of all, what other people are doing right in front of our noses.

"As we move along, the rich tone of the boatmen singing breaks the stillness," Moore is called upon to narrate at one point, thus breaking the rich tone of the boatmen singing as they ferry her across a swamp.

We don't even get to see the endlessly planned, oft-mentioned and much-heralded raid by black Union soldiers against a Confederate supply depot, the climactic campaign by which the "Negras" (as they are always being called by the "Buckras," as the "Negras" are always calling the white folks) must prove their military mettle. The raid is still pending as Charlotte's mission concludes.

Moore's previous television credits include a "Love Boat" special, "Ellis Island" and "Adventures of a Two Minute Werewolf." Dressed in frilly frocks and what looks like a doily on her head, she is most effective when coughing heavily (Charlotte, it seems, has respiratory problems) or gazing at the ceiling to play a Chopin nocturne on whatever grand piano happens to be handy. Others in the cast are equally evocative. And Beatty, a class actor who puts in a couple of brief appearances as an abolitionist preacher, looks perpetually pained -- or maybe just sleepy.

Whichever, we can sympathize.