There has never been anything quite like the conclusion of "Roots II" -- not even the conclusion of "Roots I." The final chapter of ABC's 14-hour "Roots: The Next Generations," airing tomorrow night at 9 on Channel 7, builds to one of the greatest emotional crescendos in the history of television.

The last chapter is part docudrama, part detective story, part melodrama and part pure celebration. It is also part mystery, and even though we know the mystery's outcome -- that Alex Haley will learn of Kunta Kinte and thus find the key to his ancestry in Africa -- the suspense in reaching it is still captivating.

Writer Ernest Kinoy and director John Erman move the story rapidly and grippingly to its final triumphant scenes when, in an African village, Haley hears an aged griot recite from memory a history that corresponds to tales told him in America by his relatives -- how, one day, "the eldest son, Kunta, left the village to cut a tree to make himself a drum, and that was the last time he was seen."

ABC, in its promomaniacal frenzy, has unfortunately already shown and reshown, in insistent teasers to previous chapters of "Roots II," what happens next. James Earl Jones as Alex Haley exclaims, "You old African! I found you!" It is a pleasure to report that this is not in fact the climax of the story and that there is an even more jubilant and moving moment to come. There will be hardly a dry eye in the nation when it does.

The path to illumination is not without its detours. In the first hour, Marlon Brando makes his heavily publicized TV-movie debut as American Nazi party leader George Lincoln Rockwell, whom Haley interviewed for Playboy magazine. This sequence is something of a set piece, isolated from the rest of the story, but it does contribute to the dramatic progression; Rockwell's rantings, gunhandling and spritzes into the air of a spray deodorant help shock Haley into a heightened racial awareness.

More instrumental are the exhortations of Malcolm X, whom Haley also interviewed and who is played in "Roots" by Al Freeman Jr. The 1965 assassination of Malcolm X is graphically recreated, and although the precise relevance of this within the context of "Roots" could be questioned, the scene does have the distinction of summarizing the insanity of the '60s in one harrowing explosion of gunfire.

Whether Brando is really playing a character or merely making an appearance also turns out to be beside the point, since it's a pretty transfixing turn however you look at it. The fact that it's Brando growling those racial epithets makes them all the more chilling, and clearly establishes a latter-day link to incidents of violent racism from the past seen in previous episodes.

The decisive asset of the final chapter is James Earl Jones' performance as Haley. There are few actors so capable of appearing robust on the screen. Jones makes Haley's search convincing and compelling, whether he is taking notes on a porch in Henning, Tenn. from "Cousin Georgia," or exclaiming as he spies a familiar name on a piece of microfilm in the National Archives, "Oh my God -- that's Aunt Liz!"

It is clear now that "Roots II" is probably about two hours too long, that the material could have profited from judicious abridgement, and that the decision to go to 14 hours (the original was 12) was a commercial rather than artistic one. So few decisions in television are artistic ones.

But "Roots" goes out on a grand note (with author Haley appearing for another sermonette-postscript after the drama ends) and in time it will be its grandness and not its lapses that we remember. "Roots" is a television program we will all be telling our grandchildren about.