The New York Islanders do not know how to quit. In one of the most dramatic games in Stanley Cup playoff history, the Islanders rallied from a two-goal deficit in the third period tonight to defeat the Washington Capitals, 6-4, and force a decisive fifth game Tuesday night at Capital Centre in their Patrick Division semifinal series.

Goals by Patrick Flatley, Mike Bossy and Bryan Trottier sent the Islanders surging into the lead, but a gutty call by referee Andy Van Hellemond gave Washington a chance to tie before Bossy wrapped it up with an empty-net goal.

With 30 seconds remaining, Van Hellemond awarded Washington a penalty shot when New York defenseman Paul Boutilier dislodged the goal while the Capitals were pressuring Bill Smith. Coach Bryan Murray chose Bob Carpenter to take the penalty shot and he was foiled by Smith while the crowd of 16,002 went wild.

Carpenter skated down the middle and fired the puck at Smith, who stood his ground and stopped it with his right arm. Although Carpenter declined to discuss the play afterward, it is his usual procedure in one-on-one practice situations to lift the puck under the crossbar as the goaltender goes down.

"I thought he would shoot about halfway, that's why I held my ground," Smith said. "He came in and made one or two head fakes and went to his forehand. I got it with my arm.

"In a situation like that, you can't afford to think. Goaltending is reflexes and quickness. You don't even want to know who the shooter is. You just know it's a good shooter."

"Bobby is our best goal scorer and a guy who in practice usually puts it up under the crossbar," Murray said in explaining his selection. "He didn't put it up, maybe because of pressure, maybe because Smith made a big play."

Trottier scored the game winner with 68 seconds left in regulation off a faceoff in the left wing circle, after goalie Al Jensen had made a superb glove save on John Tonelli.

Trottier, dueling for the puck with Doug Jarvis, knocked it forward, pursued it and slapped it over the stick of Rod Langway and between Jensen's pads.

"It's an instinct play," Trottier said. "The puck just went behind his stick and I grabbed it and shot it."

"We were both going in the same direction with it," Jarvis said. "The puck didn't leave the area, but I didn't tie his stick up."

During the regular season, the Capitals lost only two games when they entered the third period with a lead, 7-5 to Winnipeg and 3-2 to Boston. In each case, they had a one-goal margin after two periods, making this the first time all season they frittered away a two-goal lead in the last 20 minutes. Still, they refused to look on it as a portent of disaster.

"The winning goal came on the bounce of the puck," Langway said. "You have to live and die with these things. They're evening out. I said it would go five games long ago and now it's coming down to that.

"It's a one-game shot in our building with 19,000 people and we're going to come up large. We'll play the way we've been playing, I guarantee it."

Several thousand tickets remain for Tuesday's contest, which will determine who faces Philadelphia in the divisional final. No team in NHL history has won a best-of-five series after falling behind 2-0. Four times teams have come from two games behind to tie it, but all lost in the fifth game.

In contrast to the Islanders' 2-1 victory Saturday, this game was a thriller from opening faceoff to empty-net celebration.

After just 45 seconds, Islander Roger Kortko fired a shot that caromed off the pad of Jensen, who had come far out to reduce the angle. It was behind Jensen and inches from the goalline when Jarvis swept in from the side boards a step ahead of Flatley and knocked it clear, dislodging the net in the process. "I don't know if it had enough momentum to go across, but I was glad to see Doug get there," Jensen said.

Seventeen seconds later, Jensen came far out of his crease and lofted a loose puck into the stands, for which he was assessed a delay-of-game penalty. "I was really shocked by the penalty," Jensen said. "In the course of the playoffs, I've seen a lot of tripping and slashing go by, and then you see a penalty like that that has no effect on the game."

Murray was incensed when Gaetan Duchesne was tripped by Denis Potvin without a penalty call during the ensuing power play. Murray opened the door to the bench, screamed at Van Hellemond and then slammed it. When he continued his tirade, Van Hellemond summoned Langway and told him to calm Murray down.

Murray became even more unhappy when Potvin converted Tonelli's pass a few seconds later to give New York a 1-0 lead.

"They cry to the officials and they get the calls," Murray said. "Bill Smith and Al Jensen have thrown the puck into the crowd 30 times in this series and nothing's been called. Then Denis Potvin kicks the feet out from under Gaetan Duchesne and we wind up fighting the ref instead of playing our game."

The Capitals got back to their game, however, and took a 2-1 lead on breakaways by Mike Gartner, on a power play, and Dave Christian.

Fifteen seconds after Christian sent Washington in front, Bob Nystrom converted a Trottier pass to tie it again.

The Capitals dominated the second period, despite a double minor to Scott Stevens for holding Clark Gillies and hassling Van Hellemond.

Jarvis put the Capitals in front, 3-2, on a rebound with Smith down. Then the Islanders were hit with two penalties, to Tomas Jonsson for interference and Smith for slashing. Four seconds after Jonsson returned, the Capitals' power play clicked for the second time, with Gartner setting up Gustafsson at the right post.

Early in the third period, Jensen blocked a shot by Flatley and the puck struck the skate of Stevens and squirted across the goalline. The score ignited both the Islanders and the crowd.

"It was like an overtime goal to me," Flatley said. "There's nothing like an intense hockey game that means something, and our guys thrive on it."

After Carpenter hooked Kortko, the New York power play, best in the NHL, evened the score. Jensen made saves on both Brent Sutter and Tonelli, but after the second stop the puck just lay there for a Bossy tapin.

Trottier and Smith took care of the rest.

"It didn't look good after the second period, but our guys don't know what the word quit means," said New York Coach Al Arbour. "They discussed things between periods, saying they had to find a way to win, and then they went out and did it."