Where public television boldly went 13 years ago, pay TV belatedly goes tomorrow night. Both Home Box Office and Showtime unveil, with hoopla and fanfare, new anthologies adapted from American short stories. Robert Geller's stellar "American Short Stories" ran on PBS stations from 1977 to 1982.

HBO appears to have spent a ton of precious Warnerdollars (it is now owned by media Gargantua Time Warner Inc.) on its "Women & Men: Stories of Seduction," premiering at 9 p.m. tomorrow. By contrast, Showtime's "30 Minute Movie," premiering at the same time, looks to have been made on a much smaller budget.

Surprisingly or not, it's the modest Showtime films that are more impressive and considerably more rewarding -- The Triumph of the Shoestring. HBO's three dramas are gorgeously and glamorously produced (by movie veteran David Brown) but stubbornly unaffecting. They're like very tony fashion shows, all look and no feel.

In fairness, Showtime did not originate its "30 Minute Movies" but acquired them from the Discovery Program, a project started by Jonathan Sanger and Jana Sue Memel in 1987 to give young directors and writers an entree into the film business. David Puttnam, then head of Columbia Pictures, helped get financing from Coca-Cola, which then owned the company.

Now, Showtime is providing financing for additional films to come in the series. Based on the first three to be shown, it's a wise investment. All three are worth watching, but one, "12:01 PM," is especially good, a fascinating fantasy worthy of the original "Twilight Zone."

Myron Castleman, a blank-faced accountant, pops his eyes open and finds himself on a pedestrian island in the middle of a busy street. He looks up at the giant clock on a big building; it is 12:01.

Castleman walks anxiously across the street and into the park. A gabby man's grocery bag falls through. A fat man is plotzed with bird doody. An attractive young woman drawing on a sketch pad befriends a bedraggled panhandler. All very normal, until 12:59 rolls around. Suddenly Myron Castleman is engulfed in a bright light, plunges into darkness, goes through a kind of sonic boom and -- ouch, already.

He opens his eyes. He's on a pedestrian island in the middle of a busy street. He looks up at the giant clock on a big building; it's 12:01 again. And again. And again. The universe, it seems, is caught in an inexplicable time bounce, repeating the same hour over and over like a record needle stuck in a groove.

Only Myron Castleman, however, realizes it and remembers it. Everyone else thinks things are going along just fine.

Impossible? Prove it can't happen. This is a story about rut as human condition and ultra de'ja` vu. Myron will never be able to get a firm grasp on reality, but then, how firmly can anyone grasp anything so fragile? The tale is deftly told by director Jonathan Heap, who cowrote the script, from a Richard A. Lupoff short story, with Stephen Tolkin.

Kurtwood Smith, usually a movie heavy, has the ideal haunted Kafka look as Myron, and Laura Harrington scores quietly but effectively as Delores, the woman on the park bench who comes this close to believing him. "12:01" is the second of the three stories on the Showtime premiere; it sets off such eerie reverberations that it really should have been saved for last.

First is "Conquering Space," a sweet and pungent coming-of-ager about a 16-year-old girl (Amy Stewart) who moves from St. Louis to Cape Canaveral at the dawn of the U.S. space program in 1960. Her father, played with pristine subtlety by Guich Koock, has been lured to a new job by his crazy dream of humans one day walking on the moon.

Mark Stratton co-wrote the script with Lois Becker and directed the film, from a story by Mary Morris. The budget crunch hurts, unfortunately, during a crudely faked scene in which members of the family are supposed to be watching a rocket launch.

"To the Moon, Alice," the last story, has an inspired premise that the director and co-writer, Jessie Nelson, unfortunately abandons too soon. A homeless family of three takes shelter each night in the fakey-cozy set of a silly domestic sitcom, "Honey, I'm Home," on a dank Hollywood sound stage.

The contrast between foolish escapism and cruel fact is made bluntly yet cleverly. But then the family is tossed out and the film turns into another catalogue of abuses suffered by the homeless. One glaring flaw is the omission of black families among the homeless; only whites and Hispanics are depicted.

Karen Young as Alice, the wife, redeems the film, however, with her plaintive, heartfelt performance. She looks like a photograph by Dorothea Lange. Although it falters, this evening of "30 Minute Movies" on Showtime still can be chalked up as a captivating success.

"HBO Showcase" certainly delivers the star power for the "Women & Men" (originally "Men & Women") presentation: Elizabeth McGovern and Beau Bridges in the first story, Molly Ringwald and Peter Weller in the second, Melanie Griffith and James Woods in the last.

Unfortunately, the air is brittle with frostbite.

Bridges and McGovern work up the most warmth. "The Man in the Brooks Brothers Shirt," adapted by Frederick Raphael from a Mary McCarthy story, finds them making an unlikely interlocking on a Depression-era train enroute to Sacramento. Bridges' boyish goofiness as an instantly love-struck married salesman is wildly charming; McGovern comes close to convincing you she's a cynical lefty clinging tight to her illusions of super-sophistication.

Both these performers have pudged up a bit over the years, especially Bridges -- who, in character, says of the encounter, "If only this had happened 10 years ago. I wasn't so fat then."

Things get much leaner with the next story: "Dusk Before Fireworks," adapted by Valerie Curtin from a Dorothy Parker original and directed listlessly by the formerly flamboyant Ken Russell. Weller plays a lizardly playboy in a silk bathrobe and Ringwald (a knockout in the period clothes) is the young woman who has to decide how many of his lies she can live with.

It's the '20s, but the red radio in the man's apartment manages to play songs written in the '30s, like the Gershwins' "Love Walked In." Love never does walk in and it takes too long for Ringwald to walk out. For some reason, the story is narrated by a man, which makes no sense at all.

Finally, Joan Didion and John Gregory Dunne, those chichi movie-land magpies, take a stab at adapting Ernest Hemingway's "Hills Like White Elephants," directed in Spain (where it's set in 1925) by Tony Richardson.

Woods is wooden as an egotistic writer; Griffith is inviting and involving in that lovable, dewy-eyed way of hers as his pregnant girlfriend. They sit at a cantina and murmur ominously about "the operation," meaning an abortion, and wait for the next train.

At one point, she implores, "Could we please please please please please stop talking?" The audience is bound to be ahead of her on that one. "Hills" suffers from a problem affecting all three HBO stories; it just doesn't resonate. It's "literary" in a rigid, off-putting way.

Usually, HBO outdoes Showtime on every level. Showtime's graphics are tacky, its presentation flat, its promos among the most irritating in all of television (and people are paying to watch!). But in tomorrow night's short-story square-off, Showtime comes up the victor. The underdog has his day.