Diamond Stone dunks home two of his career-high 39 points as the freshman center led Maryland back from a 13-point second-half deficit to a 70-64 win. (Toni L. Sandys/The Washington Post)

Diamond Stone looked like a teenager possessed shortly after slamming home a two-handed dunk early in the second half Wednesday night against Penn State. He curled his fingers and talked to himself as he backpedaled downcourt, eventually flashing a wicked smile at Penn State’s back court. Stone looked straight-up scary in that moment, as if he was going to do something no Maryland freshman had ever done.

And he did. As Maryland endured its worst offensive performance of the season, Stone levitated with the best night of his young career, finishing with 39 points — 32 in the second half — and 12 rebounds as the fourth-ranked Terrapins rallied for a 70-64 win in their Big Ten opener.

Sold-out Xfinity Center was chanting Stone’s name as he walked off the floor after the win. Fans snapped photos and videos with their phones to record this piece of history — and for good reason. Stone shattered the single-game freshman scoring record of 33 set by Joe Smith in 1993. He made 10 of 15 shots from the field and 19 of 25 from the line and was a menace on the defensive end as Maryland rallied from a 13-point second-half deficit.

“I don’t pay too much mind to it,” Stone said. “I knew I was in the zone, but I wasn’t aware of any points or records.”

Robert Carter Jr. added 11 points and Melo Trimble had 10 for Maryland (12-1), which shot just 33.3 percent and was a dismal 5 for 21 from beyond the arc. Stone was simply the great equalizer, becoming the first Maryland player to score more than 35 points since Greivis Vasquez scored 41 in a double-overtime game in 2010. Stone also set the school record for free throws made in a game (19), breaking a 44-year-old record set by Maryland legend Tom McMillen. He also had the most attempts (25), beating former guard Keith Booth’s previous mark of 24 set in 1996.

As Stone blew past some of the most celebrated names in school history, his performance was only magnified by the fact that he came off the bench for a sixth straight game. At one point during his holiday break last week, he texted Maryland Coach Mark Turgeon and told him that he was embracing his new role. Against the Nittany Lions, he sprung out of his warmups and rushed to the scorer’s table when Turgeon called on him about four minutes into the game, antsy to check in and provide an energy infusion Maryland so desperately needed.

“Diamond likes the bright lights, he likes the big stage, he likes to be challenged, and we were extremely challenged today,” Turgeon said.

The Terrapins missed 13 consecutive shots at one point in the first half, with the College Park crowd groaning louder with each miss. Maryland shot just 25 percent from the field in the first half (6 for 24) and made 2 of 8 from beyond the arc. The Terrapins’ two star guards, Trimble and Rasheed Sulaimon, were bottled up and finished just a combined 1 for 9 before halftime. To make matters worse, Maryland was outrebounded 19-13 and looked sluggish as its offensive inefficiency seeped into other facets, and Penn State (9-5) took a 31-23 halftime lead.

Penn State took a 46-40 lead with 12 minutes remaining after a quick 7-0 run fueled by Brandon Taylor’s three-pointer. Stone answered with three consecutive hard-fought trips to the free throw line, and even though he made only four of the six shots, his physical play both underscored his growing maturity and set the tone for Maryland down the stretch.

As Maryland endured another cold spell — it missed 11 straight shots at one point in the middle of the second half — the Nittany Lions kept grinding. Penn State’s lead ballooned to 58-45 with 6 minutes 34 seconds remaining courtesy of five consecutive points from forward Donovon Jack.

But Stone continued to dominate even as his teammates struggled. He ripped off seven consecutive points to cut the lead to six — including a three-point play after making a steal in the open court — and Trimble swished a three-pointer to make it 60-55 with just over five minutes remaining. Trimble drove the lane on the ensuing possession and lobbed a layup attempt off the backboard before Stone finished the miss with a ferocious two-handed slam.

“I give Diamond Stone a lot of credit for how he battled,” Penn State Coach Pat Chambers said. “He made some big time plays. He’s a tough physical kid and has a lot of talent.”

After Trimble tied the game at 60 with another three-pointer with 3:49 remaining, Penn State retook the lead with a pair of free throws before Stone tied the game again with a hard finish in the lane. That put him at 34 points and gave him the freshman scoring record.

He wasn’t done. Stone was awarded a pair of free throws after being mauled following a crafty pass from Trimble and sank both to put Maryland up 64-62. After Penn State missed a potential go-ahead three-pointer on the ensuing possession, Stone helped put the finishing touches on the win by drawing yet another foul, calmly stepping to the line and knocking down both.

His front-court mate, Robert Carter Jr., nailed a three-pointer with 31 seconds remaining to push the lead to five and send Stone into further euphoria. After the final buzzer, he jumped around like the giant kid he is and listened to the crowd chant “DIA-MOND!”

“That was just a great feeling, for my school, for Maryland to be excited for me,” he said.