For 40 minutes, the Utah Mammoth looked poised to steal Game 1 on the road. Then the Vegas Golden Knights did what they do best: rally in the third period.

Captain Mark Stone tied the game on a power-play goal at 5:33 of the final frame, and Nic Dowd tipped in a point shot from Noah Hanifin just 1:47 later to give the Knights their first lead. Ivan Barbashev sealed the 4-2 victory with an empty-netter with 1:39 remaining, putting Vegas up 1-0 in the best-of-seven first-round series at T-Mobile Arena.

“We got our legs under us in the first two periods, and then just kept it going,” Barbashev said.

The Knights trailed 2-1 entering the third period. Utah had been 29-2-2 in the regular season when leading after two periods. But Vegas improved to 8-0-1 under coach John Tortorella, including the regular season.

Utah struck first with 11 seconds left in the opening period. Center Logan Cooley scored the first postseason goal in Mammoth history, beating goaltender Carter Hart. Cooley is no stranger to scoring against Vegas; he netted four goals against the Knights on Nov. 24 in Salt Lake City.

The first period also featured 10 penalty minutes, blood from uncalled high sticks, and a headbutt during a scrum.

Colton Sissons tied the game at 3:44 of the second period after a no-look backhand pass from winger Cole Smith. But Utah restored the lead 1:23 later when Kevin Stenlund threw a puck toward the net that deflected off Kaedan Korczak’s stick and in.

Stone’s power-play goal made him the Knights’ all-time leader in playoff goals, surpassing Jonathan Marchessault.

Hart finished with 32 saves. The Knights’ fourth line of Sissons, Dowd, and Smith provided both energy and offense.

“What we learned today is you have to play all 60,” Smith said. “It’s going to take every minute of every game. We just kept grinding.”

Game 2 is scheduled for Tuesday at T-Mobile Arena.