Exactly three years ago today, the Boston Celtics hosted the Washington Wizards for game two of the Eastern Conference semifinals. An electrified, sold-out TD Garden crowd roared in excitement—18,624 strong.

Diehard Boston fans knew a 2-0 series lead would put the Celtics that much closer to preventing LeBron and his Cavaliers from three-peating as kings of the East.

What they didn’t know, however, was what they were about to witness.

There’s no need for long narratives around the 2017 season, rants regarding Boston’s front office, or controversial takes about how Isaiah Thomas should still be a Celtic. On that special night, none of the noise mattered; IT4 was playing for his sister, and nothing could stop him.

The truth is, when all was said and done, Isaiah Thomas’ 53-point performance was the gutsiest display of courage I’ve witnessed out of someone in a Celtics uniform, as well as one of the most heroic and iconic performances in Boston sports history.

Before game one of the series, Thomas arrived at Logan Airport at four in the morning. He had just traveled back from Tacoma, Washington where he gave a eulogy at his younger sister’s funeral. Chyna Thomas died in a single-vehicle car crash on April 15, a day before the Celtics’ playoff opener.

Running on little to no sleep, Thomas pulled up to the TD Garden at 10 a.m. for a pregame walk-through. He went on to lead all scorers with 33 points that night, adding nine assists.

Thomas’ epic game one performance didn’t come without a little blood. A tooth injury sustained from game one led to a six-hour operation the day before game two, along with a follow-up session with his doctors the next day, hours before tipoff.

In game two of the series, Thomas exploded for 53 points—including 29 in the fourth quarter and overtime—to lead Boston to a 2-0 series lead over Washington. His fiftieth point, an AND-1 over Markieff Morris, stood as the dagger, erupting the Garden and putting the Celtics up five with a minute remaining.

The death of his sister, surgery on his mouth, Washington’s hopeless defensive strategy—nothing could stop Isaiah Thomas. He was a man on a mission. No one was going to tell him no.

In a postgame interview with TNT, an emotional IT shared out, “It’s my sister. It’s her birthday today… Happy birthday. She would have been 23 today. Everything I do is for her. And she’s watching over me, so that’s all her.”

Watch all 53 of Thomas’ points from his legendary performance below.