Boston legend Tommy Heinsohn told me before Game 1 of the Wizards-Celtics second-round series there are three Celtics he’s watched in his 82 years that make him say, “How did he do that?”: Bill Russell. Larry Bird. And Isaiah Thomas, which shouldn’t come as a surprise if you witnessed Thomas score 53 points in the Celtics’ 129–119 overtime Game 2 win over the Wizards. It’s not just the tough shots he’s hitting over defenders that provoke that kind of response. How did he do that is the recurring question of Thomas’s postseason.

We’re in only the second round of the playoffs, and perhaps this game will be forgotten in a week, or maybe even a few days. Legends are born in the NBA Finals. But Tuesday’s performance was special. It occurred on the same day as Isaiah’s late sister’s birthday. She passed away tragically on April 15 and would’ve turned 23. “The least I could do is go out and play for her,” Thomas said after the game. After losing a tooth in Game 1, Thomas underwent six hours of dental surgery Monday and spent an additional four to five hours Tuesday trying to put down the swelling. Scoring 53 points is impressive no matter the circumstances, never mind what Thomas went through personally and medically.

There are nights when a player enters the zone, and then there are nights when an entire arena reaches those heights collectively. They’re part of something bigger than one game, or one series, or one season. The player and the crowd are connected in a moment, feeding off each other in a virtuous cycle. Isaiah Thomas seemed to understand the moment he was in. “I always dream of moments like this,” Thomas said after the game. “Those are where legends are born. One day I want to be one of those guys.”

This is a Boston crowd that has seen its fair share of greatness over the decades. When it became clear that they were in the presence of something unprecedented, you could feel it. A longtime Celtics executive told me it was the loudest TD Garden had been since the 2007–08 championship team. Thomas’s layups were like power chords, his 3-pointers were like the notes of a guitar solo. I’ve never experienced a crowd roar louder. This is what Beatlemania must have been like.

Thomas scored 29 points in the fourth quarter and overtime on 11-of-16 shooting. The Wizards scored only 30. As John Wall and Bradley Beal ran out of steam, Thomas seemed to grow stronger. With the Celtics maintaining a late overtime lead, and Thomas still getting buckets, the crowd got even louder. The final moments of the game were a victory lap, and watching Thomas soak it in was like seeing a golfer walking up the 18th fairway when he knows he’s going to win the Masters.

“What else is there to say?” a perplexed Brad Stevens said after the game. “I thought he was really gonna have to gut this out one. He not only guts it out, he ends up with [53]. Pretty impressive.” Thomas scored no matter how he was utilized. It seemed like he victimized a different Wizards defender with every bucket. Kelly Oubre Jr. and Otto Porter Jr. couldn’t contain his drives, and Markieff Morris got crossed up on an ice-in-your-veins pull-up jumper.

Thomas didn’t have one of the NBA’s most efficient high-volume scoring seasons in history because of isolations, though. The Celtics use Thomas as a weapon off the ball, too. Stevens called him a “pretty remarkable” off-ball scorer, adding “he’s just a really well-rounded guy at scoring the ball.”

Thomas is as much of a menace when the ball’s not in his hands, racing around screens and flashing footwork that’d make Kyle Korver blush. He’s a speed demon, so small that he can slip through screens bigger players can’t. Thomas is so good that I sometimes wonder if his 5-foot-9 frame is an advantage. I know that’s not true, though. His size is partially why he was drafted 60th in 2011. Some guys named Chukwudiebere Maduabum and Ater Majok were taken a few picks before him. The Kings didn’t want him. The Suns traded him after a few months. The Little Guy never fit anywhere. Until he made it to Boston, and he’s only earned himself a new nickname: King in the Fourth. Thomas averaged 9.8 points per game in the fourth in the regular season and single-handedly carried the Celtics in countless games. His night on Tuesday was on an even higher level.

“It’s hard in the heat of the moment to know when to pass when you got it going like that, or when to score. And Isaiah seems so poised every time making the right decision,” Al Horford said. “After all that he’s going through, I don’t think a lot of guys would’ve even played this game. It’s something special.” Horford’s right. Thomas has turned tragedy into triumph, adversity into awe.

Back in January, Thomas told me that true greats separate themselves in tight situations. “It seems easy for the great players. It seems like they’ve seen the situation before,” he said. Again, Isaiah Thomas dropped 53 points in the city Russell and Bird once ruled. Thomas is playing on hallowed ground, and he’s made the Garden his home.