As Glenelg Country School’s Blair Byrne raced through the midfield in overtime of Friday’s playoff game against Archbishop Spalding, she kept her eyes on her twin, Regan Byrne.

Regan moved across the front of the cage, took the pass from Blair and whipped a quick shot into the net a little over four minutes into sudden-death to give the No. 4 Dragons a 7-6 victory over No. 5 Archbishop Spalding in the IAAM A Conference lacrosse quarterfinals.

The twins jumped into each other’s arms as teammates swarmed them to celebrate a victory that started on the defensive end where visiting Spalding attacked first in the five-minute overtime period.

The Cavaliers took the first shot in overtime, but Dragons goalie Natalie Eastwood made a back-handed deflection. Spalding got the rebound, but seconds later, Blair Byrne and Julia Dustin combined to force a turnover. Dustin grabbed the ground ball.

Blair Byrne gave plenty of credit to her defensive teammates for a sensational game, but she knew her sister would finish off the transition game-winner.

“I saw Regan’s defender slide to me,” Blair said, “and when I see that happen, I know how to pass it to her. I know exactly where she’s going, so I passed it to her and it was a one-on-one with the goalie which is always an amazing way to score an overtime winning goal.”

Regan Byrne finished with five goals while Blair had a goal and two assists — both to her sister.

“We probably have an unfair advantage,” Regan said with a laugh. “We work so well together. She knows exactly where to pass it to me, if I will catch it, if I won’t catch it. You won’t see many times where she throws a bad pass or I won’t catch it.”

The fourth-seeded Dragons (14-3) advance to meet No. 1 and top-seeded McDonogh (18-1) in Tuesday’s semifinals. The Eagles, who went undefeated in the A Conference, defeated Roland Park, 16-5, in their quarterfinal.

Spalding (12-5) certainly didn’t make it easy for the Dragons.

With their speed in the midfield, the Cavaliers dominated the draws, 13-2, forcing Glenelg Country to play long stretches of defense, and they jumped out to an early 2-0 lead. The Dragons didn’t take their first lead until, 6-5, with 15:29 remaining in the game.

Eastwood, who finished with 14 saves, got a lot of help from defenders Ashley Dyer, Cate O’Ferrall, Julia Dustin and Ella Dyer.

The junior goalie said her final save was a collaborative effort.

“The defense did a great job the whole game, just giving me the shots that I wanted to see,” Eastwood said. “I’m really fortunate to have such a good and confident defense that has confidence in me and they’re confident in everyone else. We’ve been practicing moments like this and I think it just came down to I was ready and I wasn’t ready to be done yet.”

After the Dragons pulled ahead 5-3 with 11:08 left in the game on three straight goals from Regan Byrne, the Cavaliers answered with their own run of three goals, two from Maeve Cavanaugh and one from Gabby Greene to surge ahead 6-5 with 3:58.

Just over a minute later, Maggie Flanagan raced past the Cavaliers defense to score a transition goal.

Cavanaugh won the next draw, her eighth of the game, but the Dragons defense held off four Spalding shots to force the game into overtime.

“That’s a great game of lacrosse,” Glenelg Country coach Paige Walton said. “Yeah, you’d love to walk into a game and win 18-2 or something, but that’s a great game of lacrosse, end to end. It was a battle from the time we started, especially when we played a ton of defense today, a ton of defense…”

The Cavaliers, who got three goals from Cavanaugh, also had a stellar defensive outing led from Maddie Wrenn, Clare McGuire and goalie Colleen Berardino, who finished with seven saves.

Spalding coach Tara Shea said her team has come a long way since falling to the Dragons, 13-11, on April 11. They fell behind, 4-0, in that game.

“We’ve come together offensively, defensively. We’re even more dominant on the draw,” she said. “And again, we’re just a little bit calmer. As many kids as we returned, we also brought in a handful of brand new players to be starters and there’s a little bit of a learning curve and an adjustment with that and, I think, from where we were to where we are now, the future continues to be so bright for this program.”

IAAM A CONFERENCE QUARTERFINAL

NO. 4 GLENELG COUNTRY SCHOOL 7, NO. 5 ARCHBISHOP SPALDING 6 OT

Spalding 3 3 0 — 6

Glenelg CS 2 4 1 — 7

GOALS: GCS—Regan Byrne 5, Blair Byrne, Maggie Flanagan; AS—Maeve Cavanaugh 3, Gabby Greene 2, Makenzie Brewer.

ASSISTS: GCS—Blair Byrne 2, Lilly Fortin; AS—Ava Baselga.

SAVES: GCS—Natalie Eastwood 14; AS—Colleen Berardino 7.