When advance notices for the debut series on this year's PBS Masterpiece Theater arrived recently, most everything seemed in order for television's esteemed outpost of the polished period piece.

As expected, it looked very British. The subject was Edmund Kean, "the flamboyant 19th-century performer" and his "high living and loving, temper tantrums and tremendous talents." The star was Masterpiece Theater productions, as well as the man who originated "Equus" on Broadway. And a review from the London Daily Express of the original showing last year on British television described it as "glorious, sexy, slap-up, send-up slapstick."

It all sounded like more genteel good times from the British tube until you noticed the name of the playwright, Jean-Paul Sartre, the somber French father of existentialism. Television slapstick by Sartre seemed about as likely as a Neil Simon lecture on metaphysics at the Sorbonne.

The result, it turns out, is quite different from conventional Masterpiece Theater fare. Like much French drama, "Kean," which airs Sunday at 9 p.m. [WETA] in the first of two parts, is a curious amalgam.

"Kean" is a 1954 adaptation of a 19th century play by Alexandre Dumas the elder. Just where Dumas stops and Sartre picks up is not hard to guess. The first half follows a fairly steady course as a stylist, drawing room comedy of manner, satirizing court life in early 19th century London. Even where "Kean" is no "slapstick" comedy. The central dramatic gist involves the complexities created by the personal infatuations of aristocratic ladies with the lower class thespian, who is at the same time the toast of London as Othello and Romeo at Drury Lane.

The central character is a dashing matinee idol on stage, and backstage is, as one character tells him near the end of part one, "a drunkard, a churl, a melancholic drowning in dirt."

As the stresses of this dual life tighten around Kean, it becomes clearer why Sartre become fascinated with the character -- for Kean is unfolding as a tragic existential victim. The climax becomes a performance of "Othello" in which a drunken Kean confuses his role with himself and launches into an impassioned denunciation of the members of the audience. As he says later, he insulted "a Prince of Wales, a peer of the realm and 3,782 others," and he describes it as "a mock suicide" in which "someone loaded the pistol and the great Kean killed himself."

Kean is confronted with the dilemma of existential man, as one Sartre commentator outlines it, in which he "allows himself to be petrified into an object by the image others have of him, by wrongs society imposes on him, or simply by self deception." That's heavy stuff for period comedy, and sometimes it's hard to tell whether the play is comic or tragic. Eventually, one concludes that "Kean" is a period vehicle on which Sartre has imposed a deep message. Once the message comes clear, "Kean" is first and foremost a drama of ideas in the French tradition. "Kean" may not be a great play, but it is a powerful statement on the human condition.

Hopkins brilliantly evokes the charismatic Kean. He often resembles that contemporary stage idol, Makhail Baryshnikov, the shadowy eyes, the long eyelashes, the blond mane and the romantic demeanor. Robert Stephens is equally authoritative in the less complex role of the Prince of Wales.

Masterpiece Theater producer Joan Sullivan says she happened on this show by accident; it didn't occur to anyone that it was a possibility for the series. "I'd like to do more works like this," she says.