You wouldn’t believe what "Buffy the Vampire Slayer" creator Joss Whedon is doing to keep details of his May 20 series finale secret from those spoilsports who would litter the Internet with them.

Absolutely nothing, that’s what.

"I can’t," Whedon told reporters last week on a conference call. "I gave up about a year ago trying to keep anything off the Internet because even if we had alternate endings, eventually you have to put together the one with the real ending [and] somebody sees it.

"The Internet, the one really downside of it for me is the destruction of surprise. However, a lot of people don’t go on it or deliberately avoid spoilers. They’re the people I’m talking to the most. They’re the people who want to see it pure, who understand that’s the best way to see a story. [As for] the rest of them, I’ve given up the fight. ... You’ve just got to just accept that now."

Whedon decided about a year ago that he was going to end the series after this season, its seventh, long before series star Sarah Michelle Gellar earned the cover of Entertainment Weekly by announcing the UPN show was officially over.

"That’s not for lack of love or lack of stories or anything," Whedon said. "It’s just pure physical exhaustion. ... I was afraid I was gonna start to slip and compromise and not care as much, and once you start doing that, it shows. It always shows. So I knew this was my last year."

And, almost as soon as Whedon knew he was going to conclude the series this spring, he knew just how he wanted to conclude it. This whole season, at 7 p.m. Tuesdays on WPWR-Channel 50, has been building up to it.

"Everybody’s sort of dealing with their insecurity about their place," he said. "The season has really been about power, or at least that’s what we started out talking about.

"The mission statement of this show is that this girl [Buffy] has power. Nobody knows. Nobody sees it. They don’t respect her. They don’t get it. But she has enormous power, and [next month’s final] episode is about that as well. This episode deals very specifically with how she decides to use that power and what she thinks of it and what it’s really for, and that to me is very important."

Beyond that, he would prefer to keep things mum. The end should be satisfying yet not preclude future projects if the marketplace demands it.

"We do not destroy the entire fabric of the universe at the end of the last episode, and some people even live, so there’s definitely an open door," he said. "For more series, a movie, you name it."

But the talked-about "Buffy’’ animated series is on hold. And if there’s another spinoff, it won’t be this fall, owing to fatigue on the part of Whedon and everyone else connected with the series as much as anything.

Some "Buffy" characters may show up next season on "Angel," assuming the WB renews that spinoff, seen locally at 8 p.m. Wednesdays on WGN-Channel 9.

"I feel pretty sure they’re gonna pick [’Angel’] up and I’m pretty sure they’re not gonna tell us that until the very last moment," Whedon said. "I can’t say for sure whether any of [the ’Buffy’ cast] will move there as a permanent thing. ... We’re sort of partially waiting for the pickup to finalize things."

Whedon said he’s pleased with how "Buffy" evolved over the years "beyond my best imaginings," that it survived its move from the WB two years ago and that even in its finale it manages to "be funny and involving and scary and really hit on things" to which people can relate.

"Most of the lessons I learned [from other series’ finales] were cautionary tales," he said. "Part of it was: Don’t be self-indulgent. I loved the end of ’MASH.’ I cried and watched it with everybody else. But ... 3-1/2 hours? Seventy minutes for the last ’Family Ties’? ’Family Ties’?!? Seventy minutes?!?

"It’s very easy to think so much of what you’re doing that you forget that what you really need to do is just turn out an episode that’s really great. ... Of course you’re paralyzed with terror that this one won’t measure up."

Whedon also is haunted by the memory of the "Miami Vice" series finale, which hooked him with NBC promos that touted: "They saved the best for last!"

"So I watched it going: ’Ooh, I can’t wait to see it. Apparently, they saved the best for last.’ And it was just sort of a lame-ass episode," Whedon said. "They lied. So I tried to save enough for the last episode that people would really feel like they went out with a bang but they didn’t go out banging their drum—they just went out making their show."

And if you know how it turns out, just keep it to yourself, OK?