NEW YORK — The man known as Mr. Smile didn’t.

As Francisco Lindor floated toward first base in the seconds after cranking an NLDS-winning grand slam, a madhouse of blue and orange exploding around him, the hero of the hour remained abnormally calm.

His face was level, stoic, like an easy sea. He did not flash a grin, pump a fist, flip a bat or roar to the heavens and beyond. He did not turn toward his dugout in jubilation. He did not exhibit a single emotion.

“Stone-cold,” Mets outfielder Jesse Winker told Yahoo Sports after New York’s series-clinching 4-1 victory over the Philadelphia Phillies in Game 4. “That guy? He’s an assassin. It’s unbelievable. He has no heartbeat.”

If Lindor’s ticker was thumping as Citi Field roared him around the bases Wednesday, he didn’t show it. The Mets’ superstar shortstop jogged his way down the baseline, his eyes fixed on the baseball cresting out of sight, nonchalantly dropped his bat and coolly began his trot as if the stadium were completely empty.

That was very much not the case.

Around Lindor, pandemonium. Adults in thrall, their bodies overwhelmed by the moment, leapt uncontrollably like elementary school children. The faces of fans, coaches and players exuded joyous disbelief. In the stands, an ocean of arms gleefully aloft in the New York night. Noise swaddled the scene, a symphony of fanatics in roar.

“Great ball players do great things,” Steve Cohen, the club’s multi-billion-dollar owner, gushed in the celebratory locker room after the game, his eyes obscured by an enormous pair of ski goggles. “So calm. He just sat there, saw a 100 mph pitch. Gone. Spectacular.”

As Lindor crossed the plate, his expression still expressionless, he was greeted by the trio of Mets he’d just driven in. None of Francisco Álvarez, Tyrone Taylor or Starling Marte could stop beaming. Marte was the first to receive Lindor. He wrapped his sirloin arms around Lindor and lifted the homecoming hero toward the sky.

Only then did a smile creep across Lindor’s face.

“He’s the f***ing man, man,” a grinning Marte, silver grills shimmering in his mouth, told Yahoo Sports after the game.

Lindor’s blast was a fitting end to a captivating, high-stress series between these two division rivals. The Phillies entered Game 4 needing a win to extend their season. The Mets, surely, did not want to trek back south for a winner-take-all Game 5.

Both clubs started crafty left-handers on the mound. Neither offense pushed through until the Phillies scraped together a run in the fourth on an infield dribbler off the bat of Alec Bohm that Mets third baseman Mark Vientos fumbled to the turf. Bryce Harper scrambled home to notch the game’s first run.

It stayed 1-0 until the sixth, until Lindor changed the story.

The Phillies sent reliever Jeff Hoffman, who had entered in the fifth after warming up multiple times in the early going, back out to start the sixth. That would prove costly. The first three Mets reached on a single, a hit by pitch and a walk. Hoffman hucked two wild pitches; his control had abandoned him. After the inning’s first out, a force at home that kept the bases loaded, Phillies manager Rob Thomson emerged to remove Hoffman.

In came Carlos Estévez to face Lindor. Estévez, a pleasant, easy-going Venezuelan the size of a refrigerator, was Philadelphia’s key acquisition at the trade deadline. For most of the second half, he thrived as a reliable late-inning option in Philly’s bullpen. His only bugaboo: a propensity to surrender the occasional home run.

Estévez started Lindor with three straight fastballs. Two missed the zone, one whizzed past the shortstop’s bat for a strike. With the count 2-1, the reliever went back to his triple-digit heater, in almost the same spot as the pitch on which Lindor whiffed.

But this pitch caught a bit too much of the plate. This pitch, Lindor did not miss.

It was the type of swing that franchises fantasize about. There is a mural, in the bowels of Philadelphia’s Citizens Bank Park, of Bryce Harper’s iconic homer in the 2022 NLCS. It will be there until the stadium crumbles.

Lindor’s grand slam will, deservedly, get the same treatment. They will play it again and again on SNY. Pictures of it will line the concourses of Citi Field. People will have shirts made. For decades, Mets fans will climb barstools, order a few and ask one another, “Remember when?”

However, the rest of the game was not merely epilogue. Philadelphia should have had a two-out rally in the eighth, but an Alec Bohm bounder over the bag was incorrectly ruled foul. Then, in the ninth, closer Edwin Díaz walked the first two hitters he faced, bringing the tying run to the plate. A strikeout of Kody Clemens and a flyout from Brandon Marsh cooled the nerves.

Díaz ended the proceedings by blazing a fastball by Kyle Schwarber. The Mets rushed out of the dugout — not toward the pitcher as teams typically do, but to the shortstop. Lindor disappeared beneath a mob of blue.

“I’m enjoying the moment. I’m living in the moment,” he said in his postgame media conference. “A lot of people are asking me why I’m not reacting, why I’m not reacting to the home runs. I am reacting, you know. I’m celebrating inside. But at the end of the day, the job is not finished until we play 27 outs.”

After those requisite outs were recorded, Lindor was a ball of joy, roaming the field with his daughter in his arms. He took approximately 100 selfies with assorted friends and family members assembled on the Citi Field grass.

He surely smiled in every last one.