WASHINGTON — The Islanders were in command and then the second period came.

Zdeno Chara scored for the first time with his new team to cap a five-goal second period, and the Washington Capitals came back to stun the New York Islanders with a 6-3 victory Thursday night.

The Islanders led 3-0 before Washington scored four goals in 5:09. Conor Sheary scored his first two with the Capitals, Garnet Hathaway tied it and John Carlson gave them the lead on the power play.

Then Chara’s slapper from just inside the blue line beat Semyon Varlamov clean, making it five unanswered goals in under 10 minutes. The 43-year-old former Boston Bruins captain was mobbed by teammates at the bench while Islanders players looked shell-shocked by the turn of events.

“Very excited to get the first goal as a member of Washington Capitals, but I returned to the bench to the guys right away because I just wanted to share that joy and excitement with them,” Chara said.

The Islanders were in command after first-period goals by Oliver Wahlstrom, Casey Cizikas and captain Anders Lee. It appeared as though Stanley Cup-winning coach Barry Trotz’s moves to put Wahlstrom in for tough guy Ross Johnston and shuffle the lines were working after losing to the Capitals on a last-minute goal Tuesday night.

Instead, the Islanders lost in regulation for the third game in a row.

“You lose two games (at Washington) and get zero points and now you’re looking up at a few teams,” Trotz said. “This ended up being a wasted two games here for us.”

The Capitals set a franchise record by starting the season with an eight-game point streak. They did so without five regulars: captain Alex Ovechkin, center Evgeny Kuznetsov, defenseman Dmitry Orlov and goaltender Ilya Samsonov missed a fourth consecutive game because of COVID-19 protocols, and center Lars Eller was out with an upper-body injury.

“We felt good about our team, we felt good about the depth and the amount of guys that could really step in and not just fill a role but excel,” Carlson said.

Vitek Vanecek made 27 saves in his fifth consecutive start in net, Tom Wilson scored an empty-netter with 18.7 seconds left and the Capitals remained unbeaten in regulation under first-year coach Peter Laviolette.

“A lot of teams don’t come back from 3-0,” Hathaway said. “It’s a big stepping stone for us, especially in the locker room and all the guys we have in our lineup right now.”