OK, so "Buffy the Vampire Slayer" is going to meet Dracula in the show's fifth season premiere (Tuesday, 7 p.m., Ch. 30), but what fans really want to know is — what's the deal with Buffy getting a little sister?

"Buffy's" ever-evasive creator/executive producer/writer, Joss Whedon, isn't giving up much on this point, except to say that, yes, Michelle Trachtenberg is joining the cast as Dawn Summers. Which is sort of odd, given that Dawn is a teenager and, before she shows up at the end of Tuesday's episode, Buffy has never had a sister before.

"She's going to have a sisterly relationship with Buffy," Whedon said in a recent interview with the Deseret News. "We wanted to bring in somebody of a different age to sort of give us a different perspective on everybody's lives, and that's as much as I can say."

We do know, however, that Dawn will indeed be Buffy's sister. Somehow. That Buffy and her friends are going to have memories that include her. That Dawn plays into this season's big story arc.

"For all intents and purposes, there is a Dawn Summers that has always lived and shared a house and shared parents (with Buffy)," said supervising producer David Fury. But it's going to be at least five episodes before the mystery will begin to be unraveled.

As for Trachtenberg, she couldn't be more pleased to be on the show.

"It is very exciting," she said. "I've been a fan of this show forever. It's sad, because I'm like a walking encyclopedia (of the show). You ask me a question, I can not only tell you the answer, but I can give you a little history there, too."

And she said the "Buffy" cast members have been very helpful, particularly Gellar, with whom she had worked on "All My Children."

"Sarah was always really very supportive, and that was really helpful," she said.

OTHER DEVELOPMENTS: Elsewhere on "Buffy" this season:

— We can expect to see more of Harmony, Spike's vampire girlfriend. (She's actually been on the show off-and-one since the first episode, when she was a member of Cordelia's snotty group of friends.)

— There are no plans to bring back Willow's ex-boyfriend, Oz the werewolf (Seth Green).

— Amy, the witch who turned herself into a rat two seasons ago and (with the exception of a brief moment) has remained that way ever since, may get de-ratted this season. "We're talking about it," Whedon said. "We're all ready to see Amy again without the fur."

— It's possible that we'll also see some history on the show's resident evil vampire, Spike (James Marsters).

"We may even see the origins of Spike. It's about time," Whedon said.

But we won't have to worry about Whedon reforming Spike. "Spike is never going to be a nice guy," Whedon said. "He may be a sympathetic guy, but never a nice one."

— We will learn why Tara botched the spell during the battle against Adam — and more. "She does have a secret," Whedon said. "That secret will be revealed . . . in the first half of the season."

— Expect to see flashbacks to other slayers. "We are going to look a little bit more into the history of past slayers and stuff like that," Whedon said.

And, while we may not see the original slayer (who appeared in the dream sequences in last spring's season finale, "Her visit will affect the whole season."

— Xander (Nicholas Brendon) is going to be able to move out of his parents' basement.

"Xander will be finding himself this year and becoming successful in a career — growing into an adult role, more or less," Fury said. "It's in the skilled-labor industry, but it's one in which he shows a certain amount of creativity and ambition and he kind of is devoting himself to it and following through on something instead of just skipping around from job to job."

— Spike's (and Angel's) old vampire girlfriend, Drusilla, will be back this season. She'll actually make her first appearance on "Angel," but will recur on both shows.

— Buffy is once again going to ask Giles to be her Watcher. And they may seek an understanding with the Council of Watchers, which they quit two seasons ago.

"Giles at some point may require the resources that the Council provides," Fury said. "So we're talking about a possible episode of Giles and Buffy going to England to the Council demanding re-entry into the Council but on their terms."


E-MAIL: pierce@desnews.com