They were the only souls screaming inside Nassau Coliseum, cutting through the clatter of feet trudging up aisles, and yet amid the throng of Washington Capitals near center ice, few seemed to notice the silence. Some circled around the periphery, slapping every back within reach and bumping every fist. A cup of beer crashed into defenseman Brooks Orpik’s face, on the opposite cheek from where a skate had sliced open his skin. And somewhere inside that pack of white sweaters, even Nicklas Backstrom — their aw-shucks top-line center, their magic-making hero in a 2-1 overtime win Tuesday night — cracked a smile.

Moments earlier, more than 11 minutes into another extra period inside this thundering building against the New York Islanders, Backstrom had gathered the puck along the half wall, his back to the net, and surged into the middle. Forward John Tavares, the man who needed only 15 seconds of overtime to tilt Game 3 in the Islanders’ favor, had fumbled his stick, so Backstrom found a sliver of space, rocked onto his heels and fired. The puck hissed around teammate Joel Ward, who again had screened goaltender Jaroslav Halak in traffic. Soon, the complexion of these Eastern Conference quarterfinals — and really, the Capitals’ season — would finally swing in their favor.

Backstrom’s overtime strike propelled the Capitals to a life-saving victory in Game 4. Four times they had met the Islanders on the ice during the regular season and playoffs, and three times they slunk away disappointed. Finally, facing the grim reality of moving one loss from elimination, the Capitals had instead evened the series and rocketed themselves back to Verizon Center for Game 5 on Thursday night.

“It’s going to be a good feeling coming home again,” Backstrom said.

Inside the visiting dressing room, while Backstrom unwrapped tape from his shin guards and stuffed his skates into a bag for the late flight south, defenseman Matt Niskanen watched in awe. Backstrom had already notched the key faceoff win that led to forward Alex Ovechkin’s first-period strike, his fifth point in four games against the Islanders. Backstrom logged 25 minutes 19 seconds, more than any other forward on the ice. He again had yanked the Capitals back from the ledge and pulled them into a party.

The Post Sports Live crew debates whether the Washington Wizards or Capitals will make it farther in the playoffs. (Post Sports Live/The Washington Post)

“Sometimes you wonder,” Niskanen said, “if the rest of us are playing checkers and he’s playing chess.”

Given the shot Backstrom bombed from inside the blue line, his third straight outing with a goal after entering the postseason without one in 23 games, it certainly seemed as much. But the Capitals needed much more to avoid a 3-1 series deficit. They handled three penalties whistled within 5:12 during the middle period. They withstood 37 shots pelted at Braden Holtby, another round of target practice against their unflappable goaltender. They survived Orpik gushing blood, forward Casey Cizikas’s equalizer 12 seconds before the first period ended and another night spent blanketed by the jeers of the crowd that left silenced.

“I don’t want to say anything bad about them, because it’s a good atmosphere here,” Backstrom said. “But usually it gets quiet when the road team wins.”

The Capitals escaped from Ovechkin’s early tripping penalty thanks to several blocked shots from defenseman John Carlson and snuck away from an apparent too-many-men minor when forward Brooks Laich climbed over the boards too soon. The sellout crowd, replicating the booming chants that drenched the Capitals two days earlier, howled for a call but got nothing. Soon the building fell silent as Washington, for the first time in the series, scored the first goal.

Forty-five seconds after Ovechkin broke from the penalty box, Backstrom won an offensive-zone faceoff and ushered the puck behind him to Carlson. Carlson danced into the middle and cranked a shot toward traffic, where both Ovechkin and Ward had stationed themselves in a line, members of the only trio Coach Barry Trotz hadn’t tweaked from Game 3.

The puck reached Ovechkin first, so he reached his stick across his body and flicked it in stride. Turning across his body to watch, he saw Ward swing his hips in front of Halak, opening a lane at the last second, and the puck struck the net. Ovechkin whipped around and bolted up the ice, celebrating just his third goal in his past 13 road playoff games.

“I thought Nick Backstrom was all-world today,” Trotz said. “He was outstanding. And Ovi, he was a big load on the one goal there. The tip, great stick.”

Before long, though, the jubilation turned into a soul-sucking sequence right before intermission. Battling for a loose puck in the crease, Carlson tumbled backward and cut Orpik’s cheek. Orpik fled into the tunnel, trailed by trainer Greg Smith, but eventually returned.

Then with the clock winding down, forward Cal Clutterbuck cut into the slot and hammered an initial shot that Holtby saved, but Cizikas arrived in time and punched back the juicy rebound.

Washington emerged unscathed from a briar patch of penalties during the second period — two minors on forward Tom Wilson and a delay of game against defenseman Mike Green — and the pace turned breakneck from there. Yet once again three periods proved useless for finding resolution, and to avoid a fourth such loss here this season, the Capitals needed more magic from their center. They needed Backstrom to call checkmate.

“To be honest with you, it’s a good job by Ward in front of the net there,” Backstrom said. “Without him there, it wouldn’t be a goal. I would say it’s his goal.”