Vegas had a two-man advantage for 1:09 early in the third, but couldn't get the puck past Braden Holtby.
The Golden Knights trailed 3-2 entering the final 20 minutes but couldn't net the equalizer despite a 15 shot barrage.
They may have everyone available, which didn't seem likely after Game 2, when there were questions about the health of center Evgeny Kuznetsov. The game immediately took on a nastier tone, and the teams played 4-on-4 hockey moments later after a prolonged scrum led to two penalties.
Alex Ovechkin got his first Stanley Cup Final goal with a second period power-play strike.
Gerard Gallant did not match lines at home for Games 1 and 2, so don't expect the Vegas Golden Knights head coach to be anxious about who plays against who when the series shifts to Washington for Games 3 and 4.
They'd love to have their leading scorer in the lineup Saturday night in Washington, but with superstar captain Alex Ovechkin and several top players producing and filling the void, the Capitals are built to handle life without Kuznetsov if it comes to that.
Philippines say it protested China 'harassment' of navy boat
The comments came after China's foreign ministry expressed Beijing's "strong dissatisfaction" with a FONOP carried out on Sunday. He added that the area was regarded as worldwide waters and many countries wanted to exercise their freedom of navigation.
Zidane steps down as Real Madrid coach
Arsene Wenger has revealed he turned down Real Madrid on multiple occasions and says he wants to be "tested" in his next role. We always want more from the players, and a moment comes when I can not ask them for more.
National Donut Day: How to get a free Dunkin' Donut on Friday
It's nearly the weekend and what better way to start it than by getting a free doughnut! That's while supplies last, of course. During World War I, The Salvation Army's "Donut Lassies" served the delicious treats to American soldiers on the front lines.
James Neal and Shea Theodore replied for the expansion Knights. His puck-moving skills helped stymie Vegas's feared forecheck, like the head fake and backhanded pass that he threw with 40 seconds remaining and opposing goalie Marc-Andre Fleury pulled.
Holtby went into the third period with 22 saves and Fleury had stopped 17 shots through two periods. Washington probably should have won that game last night.
Vegas Golden Knights forward Ryan Reaves landed a punch to Tom Wilson's face during Game 2 of the Stanley Cup finals. Melrose said Game 1 had plenty of mistakes, but it was entertaining, and it stood out for the Golden Knights' speed and for their penalty kill. The Aces are the new Las Vegas franchise in the WNBA, and will play their games inside the Mandalay Bay, which is across the street from the spot of the new Raiders stadium. The Golden Knights are 6-2 on the road in the playoffs.
The Capitals opened the playoffs with two losses to Columbus before roaring back to win four straight. Over is 4-1 in Capitals last 5 vs.
Eller signed a five-year, US$17.5-million contract extension in February, and now has the same amount of goals (six) in these playoffs as he did in the first 50 post-season games of his career. That's the type of save the Capitals need in order to win a first-ever Stanley Cup.
But starting when Kuznetsov exited down the tunnel-taking with him an 11-game point streak, longest in the playoffs league-wide since 2010, and the breath of every Washington fan back home-the Capitals were able to access something deeper.