Tonight, the Washington Capitals will play the most important game in the 11-year history of the franchise.

No discussion. No debate. No vote.

No other nominations.

This is it.

Not just because it is the first time the Capitals have been involved in an absolutely, positively final game of a playoff series. And not just because the Capitals have squandered their 2-0 advantage. But also, and maybe even mostly, because their opposition is the New York Islanders.

Through the first half of this decade the one, true dynasty in professional sports are the Islanders. During those five years they won the Stanley Cup four times and finished second once. They have lost one playoff series in their last 20; in two of those 20 they beat the Capitals handily. In the playoffs they are close to invincible.

It means nothing that the Islanders lagged 15 points behind the Capitals in regular season. It means little that the Islanders lost four of the seven games the two teams played during regular season. That was then. This is now.

This is the playoffs. And the playoffs mean everything.

The Capitals have beaten the Philadelphia Flyers in the playoffs. Last year. Swept them. But they never have beaten the Islanders. The Islanders stand in their way like a wall. For the Capitals justifiably to claim a place on the elite shelf of the NHL, they must beat the Islanders tonight.

They can finally, declaratively make good on the promises of their last two seasons. They can shatter the windows of so many horrid finishes and sweep them down the chute of ancient history. They can confront the legend -- and in so doing confront themselves -- and not back down.

"This game," David Poile, the general manager, said nervously, "will be the ultimate test to see whether the Capitals can get over the hump or not."

Heroes. Or zeroes. Their call.

Shortly after the Capitals double-overtime victory last Thursday that seemingly guaranteed the series, defenseman Larry Murphy cautioned that his team would be wise to approach the third game venomously. "When you get (the Islanders) down, you have to kick them," he said. "Down two, losing both in overtime, any normal team would be left for dead. Not them."

The Capitals and Islanders have played four games as close as grapes on a cluster. The scores have been: 4-3, 2-1, 2-1 and 6-4, but the "6" was an empty-net deal with 16 seconds left. Two of the games have gone into overtime; the others were decided late in the third period. Both teams won their home games. Perhaps the Islanders' victories were more impressive, because they came when a single loss would have meant elimination, and because they had to rally from 4-2 down after two periods in the fourth game against a team that had entered the third period leading by two or more goals 24 times this season, and was never beaten. Yet as even as this has been, the team that finally wins might not be the better team; there might not be a better team.

Still, if you believe in momentum, you must believe that the Islanders have it. The Capitals could have won the game on Saturday night in Long Island. They were tied, 0-0, going to the third period. They should have won the game the next night. A good team is supposed to hold a two-goal lead for 20 minutes.

"I guess you could say we blew the game," Murphy ruefully conceded. "We certainly gave it away."

"It really hurts," Bryan Murray, the crestfallen coach, said after watching his team dissolve. "It's devastating to be up, 4-2, and be in a position to win a series in the other guy's building -- and not be able to do it."

For the second game in a row the Capitals grew a shell and crawled into it. "We were too passive," said Murray. Everyone connected with the Capitals saw it happen. But no one could change it. "We start thinking about the end of the game, that we've got the game won," said Mike Gartner, the Capitals' best playoff goal scorer. "All of a sudden, we're not playing to win anymore -- we're playing not to lose."

For $64,000, and the right to advance to the second round: Why?

"I don't know," Murphy said glumly. "We didn't want to. It wasn't our game plan. We just did it." He groped for a reason. "I think maybe it's our lack of playoff experience. This is the first time this franchise has ever been in that situation."

This situation: one game away from beating the Islanders, the experienced Islanders, the legendary Islanders. At their place.

The Capitals are capable of winning this series.

Are they willing to? Or does the prospect of actually beating the Islanders scare them?

"(The Islanders) were on a real high," Murray said of the third period. "We didn't handle it very well. I think we're now faced with a team that's going to have a very high level of play. They've now got the shot in the arm they didn't have going back to Long Island. The only fortunate thing we have is we're going back home. There will be a lot of noise, and our guys pick up on that. Any edge they might have will be offset by us having the home ice."

On the notions of momentum and home ice let us briefly seek the counsel of Fred Shero, newly employed by the Capitals as a sort of eminence grise for the playoffs. Shero on momentum: "19,000 people crush momentum." And Shero on home ice: "Home ice is worth a goal."

In a one-goal series, one goal is all you need.