RALEIGH, N.C. — The Islanders, so nearly, returned to New York with home-ice advantage and momentum in the series.

Instead, they got on a plane back to Long Island searching for answers after a gut-punch 4-3 overtime loss featuring a blown third-period lead, a pair of uncharacteristic goals let in by Ilya Sorokin and a Jesper Fast game-winner packed with controversy, with what seemed to be a Jordan Martinook high stick on Scott Mayfield that went uncalled in the lead-up to the goal.

The first playoff game at UBS Arena on Friday night is now an absolute must-win for the Islanders, who need to find an answer for Carolina’s speed advantage and ensure that this loss is not the backbreaker to their season.

“We just gotta find a way to score that extra goal,” Noah Dobson said. “We had lots of opportunities. It didn’t pan out for us tonight. Just gotta get ready for Game 3, regroup.”

It looked as though the Islanders would leave PNC Arena with a win after Brock Nelson gave them their first lead of the series 9:18 into the third period, burying a wrist shot off the rush.

But the lead did not last long.

Just 4:01 later, Jaccob Slavin tied the game up for Carolina, beating Sorokin on a tight-angle wrist shot that banked off Sorokin’s back and in.

The Islanders did enough to get the game to overtime, killing off Ryan Pulock’s tripping penalty late in regulation.

But in the extra period, Fast set the building alight with the winning goal as Mayfield seemed to take himself out of the play, protesting to the referees after Martinook caught him up high.

Mayfield did not speak to reporters after the game, with the Islanders saying he was getting medical attention, but the Islanders were less than thrilled with both the call and the power-play disparity, which saw the Hurricanes get 9:18 at five-on-four while the Isles did not get any time at all.

“Other than [during] a four-minute kill, we didn’t get a call all night,” Matt Martin said.

For the first time all series, the Islanders generated some sustained offensive momentum in the third period, and seemed to have the better of Carolina at five-on-five.

But the Canes’ underlying speed advantage and overall relentlessness were too much.

Even when the Isles seemed to have the run of play on their side, Carolina was never out of it. It’s hard to make a speed disadvantage go away for good.

The Isles seemed to find a way around that for a stretch on Wednesday, going into the third period with the game at their fingertips after Mathew Barzal tied the game at two with a wrist shot off the rush with a hair over 20 seconds to go in the second and retaining momentum in the third with Nelson’s goal.

“I thought we made more plays tonight,” coach Lane Lambert said. “I thought we played fast, I thought it was a good hockey game.”

Just like on Monday, Carolina was ahead within minutes of puck drop, this time with Paul Stastny deflecting Slavin’s tight-angle shot past Sorokin for a 1-0 lead.

A dominant first period for the Hurricanes quickly led to the Islanders’ emotions running hot, with Cal Clutterbuck throwing a legal but hard hit on the Hurricanes’ Sebastian Aho and Martin illegally pinning Jordan Staal to the ice with his knee.

The latter led to an all-out brawl in the Islanders’ crease at the first period’s expiration, an interference penalty for Martin and an uptick in the temperature of the series as a whole.

The Islanders made it through that penalty, but not the next one — a high-sticking double minor on Samuel Bolduc.

With the penalty winding down, Stefan Noesen chipped the puck into the Islanders’ zone, where it went off Sebastian Aho’s stick and took a strange bounce past Sorokin.

That is, the Islanders’ Sebastian Aho.

That could easily have been it for the Islanders, especially with the ice tilting heavily towards Carolina at that point. But Kyle Palmieri’s backhand goal at 10:46 of the second pulled them within 2-1, and Barzal would soon tie it up.

But that wouldn’t be enough, and neither would the go-ahead goal from Nelson.

“We had the lead in the third and gave it up,” Martin said. “Didn’t find the goal in overtime. Sometimes that happens. We just gotta regroup, like I said, forget about this one, get ready for the next one.

“And if we take care of business at home, it’s a 2-2 series. We come back here and try to win.”