Don't expect much ceremony when Ted Koppel signs off.

The closing thought with which he ends each "Nightline" will take the form of a farewell Tuesday. Then, one last time, he will likely say, "For all of us here at ABC News, good night." And it will be over: almost 26 years as "Nightline" anchor and a 42-year hitch with ABC.

"There is nothing precipitous about this," notes Koppel, who announced his plans in March. "It's time to give a new bunch a crack at this."

Now 65, he's not retiring. ("I'm not telling you goodbye; it's au revoir," he offers gamely.) After a few months, he aims to be back at work in a venture with longtime executive producer Tom Bettag, who's leaving "Nightline" too.

While Koppel declines to discuss what might lie ahead, Bettag is a bit more forthcoming, confirming they have talked with HBO about a series of documentaries (no deal is yet in place).

But wherever Koppel settles next, Tuesday marks the end of an era. And not just for "Nightline," but across network news as he joins three other giants who, in the past 12 months, have left the evening newscasts they anchored for decades: NBC's Tom Brokaw, CBS' Dan Rather and the late Peter Jennings on ABC.

Even so, with Koppel and "Nightline," there's a difference: He was there at the creation.

And though Koppel's on-air presence has diminished — in recent years he was anchoring just three nights per week — he has always set the tone for "Nightline," which since March 1980 has stood its ground against the twaddle of so much TV news.

Natalee Holloway? When mentioned to Koppel as a poster child for News Lite, her name didn't register until he was prompted with: "the teen who went missing in Aruba."

That's reassuring. But when Koppel leaves "Nightline," will its fluff filter be leaving with him?

On Nov. 28, a triumvirate of Martin Bashir, Cynthia McFadden and Terry Moran will take over. And most nights, the program will cover several stories, not just one in-depth, as before.

Multiple anchors! Multiple reports! It seems like a whole-hog reimagining of "Nightline."

"The challenge over the years, and the challenge now, is to keep changing the program without altering it," says Koppel.

He points to its evolution since its birth, when then ABC News President Roone Arledge transformed coverage of U.S. diplomats taken hostage in Iran into a broad-based late-night fixture.

Predating CNN by several weeks (with MSNBC and Fox News Channel still unimagined) "Nightline" was a fresh alternative to late-night talk and old movies.

As anchor, Koppel, who had been at ABC News since 1963 and its chief diplomatic correspondent for a decade, proved right away to be the ideal choice. A star was born at 40.

And completing the "Nightline" equation was the recent breakthrough in satellite transmission that made possible "intercontinental salons" — an interviewing form Koppel largely invented.

"What was thrilling during that first year to us and to the audience was the technology," he recalls. "Being able to orchestrate a conversation among three people — in Moscow, Tehran and in Washington — was unprecedented. Just being able to do that was enough to excite people in 1980 and '81."

But the chosen subject matter brought substance to the form. AIDS, the prison system, and racism were among the thorny topics repeatedly addressed.

"Why? Because those are desperately important issues, and you need to keep reminding the public," Koppel says.

The mission of "Nightline" was lofty, even defiant. And the public responded. As recently as the mid-1990s, "Nightline" was edging out CBS' "Late Show with David Letterman" for first place in its time slot, averaging more than 6.9 million viewers.

"Our legacy," says Koppel, "is that a serious news broadcast can be successful on all counts, without catering to anyone's baser instincts. `Nightline' has made a lot of money. It has been successful in terms of viewership, awards and accolades. But most important to me, it's been successful in not ever having to lower its standards."

As they outlined their eventual departure, Koppel and Bettag put forth a five-year transition plan in 2000.

But this succession strategy, which would have phased "Nightline" correspondent Chris Bury into the anchor seat, was derailed in early 2002 when ABC was caught wooing Letterman. Although "Nightline" still outdrew Letterman's "Late Show," ABC executives worried that their program wasn't a favorite of the younger viewers many advertisers prefer. But then Letterman stayed at CBS.

The whole episode riled Koppel, who said ABC's scheme to evict "Nightline" had caused "collateral damage" to the program.

Now he insists he is "delighted that at least the network is willing to give the news division a chance to keep 'Nightline' going."

But to save "Nightline," will the network be destroying it?

Even in the face of what seems like drastic changes, Bettag voices cautious optimism. In particular, he says, the three-anchor format may now be the best option: Koppel would be a hard act for one person to follow.

"As long as the quality is there," Bettag says, "a different kind of broadcast is not necessarily a bad idea."

And as the days count down to his no-frills exit, Koppel agrees.

"I think at its best, 'Nightline' has been able to inform and entertain simultaneously," he says. "I see no reason why it can't go on doing that."

"Nightline" airs at 11:35 p.m. EST.