Mike Knuble banged in a rebound of his own shot at 6:40 of the second overtime period to thrill the home fans and give the Philadelphia Flyers a 3-1 series lead over the Washington Capitals on Thursday night.
Jeff Carter scored twice, while Daniel Briere notched his NHL-best fifth goal of the playoffs in the 4-3 victory.
Nicklas Backstrom, Alexander Semin, and Steve Eminger replied for the Capitals. Alexander Ovechkin had two assists but was held without a goal for the third consecutive game, his second longest drought of the season.
The series will return to Washington for Game 5, with the next game Saturday at 1 p.m. ET.
The Flyers put sustained pressure on the Capitals leading to the winning goal, with Scottie Upshall and Knuble taking shots on Washington goalie Cristobal Huet.
"It's an unbelievable feeling to score in this town and hear the building go nuts," Knuble said. "You pinch yourself. You can't believe it's happening."
Huet finished with 42 saves, four more than Philadelphia counterpart Martin Biron.
Philadelphia had tied the game midway through the third on Briere's marker, finally scoring on the power play after six opportunities.
Washington went 2-for-4 with the man advantage.
"You take it home and have to take care of business there," Capitals coach Bruce Boudreau said. "They counted us out after Game 2. They counted us out after Game 3. I'm sure they'll count us out now. When they had to win seven in a row, they did it so don't count us out."
The teams scored early and often before goals became scarce over the last 40 minutes of play.
"I thought the game got more and more exciting," Briere said. "A lot more chances were being created in overtime."
Carter put the Philadelphia faithful in a frenzy just 42 seconds into the game when his backhander beat Huet. Upshall and Knuble beat the Washington defence to the puck to set up the goal.
After a skirmish between the teams resulted in a Washington power play, Ovechkin found rookie Backstrom all alone in the slot for his first career playoff goal at 2:41.
Washington took three consecutive penalties, but the Philadelphia power play couldn't click. The Flyers then got burned after taking two successive penalties.
Backstrom fed Semin with a cross-ice pass through the slot for a 2-2 tie just 13 minutes into the game.
Carter got his second of the game after an extended flurry late in the period, set up on a nifty pass from Jaroslav Modry. The defenceman was playing two days after learning that his father had died from cancer in his native Czech Republic.
Semin was instrumental in the play that gave Washington a 3-2 lead early in the second period, finished off by Eminger. It was a lead that would hold up for over a period, thanks to a huge save by Huet later in the second.
Caught out of position after an initial shot, Huet dove to knock down Upshall's followup attempt with this glove.
Meanwhile, Ovechkin had an empty net to put in a rebound for a two-goal lead, but couldn't find the mark with the bouncing puck.
The lead evaporated soon after the Capitals took their second penalty of the game for too many men on the ice. Briere was alone at the left post for an easy putaway of a pass from Mike Richards.
One game after Philadelphia crashed into Huet with regularity, Washington's Viktor Kozlov took a crucial penalty with just under three minutes left in the third for colliding with Biron. The Flyers peppered Huet with shots but could not break the tie.
Both goalies finished with 11 saves in the first overtime. Biron extended his right pad to foil Washington defenceman Tom Poti, with Joffrey Lupul's bid to end the game denied by Huet.