SCHENECTADY, N.Y.—When Sarah Vaillancourt scored her first goal in the third period, ending over 48 minutes of scoreless hockey at Messa Rink in Schenectady, N.Y., it seemed reasonably certain that top-seeded Harvard would squeak by rival Yale and move into the finals of the ECAC Tournament. When she scored for the second time, in sudden-death overtime, there was no doubt, and the Crimson escaped with a 2-1 win.

In between Vaillancourt’s goals, Harvard’s title defense was jeopardized when the Bulldogs managed to keep their season alive with a desperation tally with 14.2 seconds remaining in regulation.

With the team clinging to its narrow one-goal lead with time winding down in the final period, sophomore defender Lindsay Weaver went to the box for tripping at 18:27. Already up a skater, Yale coach Hilary Witt pulled junior goalie Sarah Love with 42 seconds left to create a 6-on-4 edge. The Bulldogs swarmed the net and got the equalizer when Jenna Spring poked the loose rebound of an Erin Duggan slapshot though the five-hole of junior keeper Ali Boe.

Despite ranking as the third most effective power play in the country entering the day, Harvard struggled throughout the game to draw penalties, and failed to convert on all four of the opportunities it earned in regulation. But the unit finally broke through for Harvard’s game-winner.

When Yale was called for a careless too-many-men penalty 11:15 into added time, the Crimson’s lethal top power-play unit was offered a chance at redemption. After Love was forced to rebuff several dangerous looks, the puck came back out to junior forward Julie Chu at the point. Chu cycled it to Vaillancourt at the left face-off circle, who stepped forward before rifling her shot inside the near post for the victory.

The Crimson controlled the run of play in the opening two frames and boasted the majority of the goal-scoring chances, but could not put one past standout netminder Love and the Yale defense.

“Throughout the game we were just trying to chip away,” Chu said. “The key is to not be frustrated with that.”

At the same time, Boe and the Harvard blue liners stood equally firm, keeping the game knotted at zero for the majority of the first two and a half periods until Vaillancourt broke through.

The speedy freshman kicked off the first scoring play when she gathered the puck at center ice and carried it ahead of the defense, only to have her shot deflected over the net by Love. Strong fore-checking by senior tri-captain Nicole Corriero kept the play alive, as she brought the puck from behind the net beside the right post and pushed it through the crease. Chu tipped the puck out to Vaillancourt—who remained in the action after her initial offering was turned away—and the winger parked it in the back of the net.

“Usually I have a bad habit of keeping going instead of stopping in front of the net,” Vaillancourt said. “This time I did and Julie and Nicole worked hard to get the puck back in front and I was standing there.”

Named the conference’s Rookie of the Year the night before, Vaillancourt paced the Crimson attack all afternoon, firing a team-high 11 of the squad’s 39 shots on goal.

Chu was the other major contributor on offense, with two assists, bringing her into a tie for third place nationally in that category.

With the win, Harvard advanced to face second seed Dartmouth, which overcame St. Lawrence by a 4-2 count in the late semi-final. The final will be played at 2 p.m. on Sunday.

“I anticipate our team is going to come out flying tomorrow,” Harvard coach Katey Stone said.

—Staff writer Jonathan Lehman can be reached at jlehman@fas.harvard.edu.