HANOVER, N.H. — Junior Sean Sullivan lined a single to left-center to score classmate Steffen Torgersen from third in the bottom of the 13th inning, lifting Dartmouth (12-20-1, 8-6-1 Ivy) to a 2-1 victory over Brown at Red Rolfe Field at Biondi Park. It was the longest game by innings for the Big Green in 15 years.

Sullivan may have provided the walk-off hit, but sophomore Austen Michel (3-1) was the star of the game, twirling seven innings of one-hit, scoreless relief to earn the victory, striking out four along the way. The right-hander entered the game with a man on and nobody out in the seventh and proceeded to retire all but two of the 23 batters he faced — one reaching on an error — including the last 17 in a row.

Torgersen led off the 13th with a line single to right, his second hit of the game. When freshman Bennett McCaskill bunted him over to second, it was just the fourth time all afternoon that Dartmouth had a runner advance that far. Sullivan then hit a 1-1 fastball and drove it toward the gap in left-center, allowing Torgersen to score easily with the game-winning run and give the Big Green their second walk-off win in the series.

For the first five innings, Dartmouth senior Clay Chatham and Brown sophomore Will Tomlinson were engaged in a scoreless duel. While Tomlinson was perfect through four innings and face the minimum over those five frames, Chatham had some occasional trouble, none bigger than in the second.

Parke Phillips, Joe Lomuscio and Hunter Carey all hit solid singles to start the inning, loading the bases with nobody out. Yet Chatham was up to the challenge, inducing a shallow fly to right, getting the second on strikes and the final out on a routine fly to left.

The Bears stranded a runner on second in the third, but broke through in the sixth when Sam Grigo led off with a single, took second on a wild pitch and scored on another Phillips base hit — his second of three on the day — for a 1-0 Brown lead. That ended Chatham’s term on the mound, having thrown five-plus frames while yielding seven singles without a walk to go with seven strikeouts.

Sophomore Michael Parsons relieved Chatham and set down the next three batters to keep Dartmouth within a run. That 1-0 deficit was as short-lived as it could get with junior Nate Ostmo crushing the first pitch of the bottom half of the frame halfway up the netting beyond the left-field fence for a solo home run, his third of the season. The Big Green threatened to score more thanks to an error and a hit batter, but Tomlinson regrouped and got the final two outs to preserve the tie.

When Parsons walked the leadoff batter in the seventh — the only free pass issued to Brown — Michel was summoned from the bullpen and needed just six pitches to retire the side.

The Bears, meanwhile, lifted Tomlinson after just 61 pitches, having allowed just one run on two hits without a walk and seven strikeouts. Dante Bosnic was just as effective out of the pen, tossing two shutout innings on one single. J.J. Sliepka pitched a scoreless ninth before yielding to Brennan Vasquez in the 10th.

Michel had a little trouble come his way in the eighth, allowing a single to Phillips before a double-play grounder was booted for an error, putting runners on first and second with one down. The miscue didn’t even register with the reliever as he got a fly to left and a grounder to second to end the inning. No other Brown batter reached base again.

Dartmouth tried to put together a two-out rally in the 11th when junior Matt Feinstein was hit by a pitch and senior Kyle Holbrook walked — the first unintentional walk drawn by a Big Green batter in 39 innings — extending his streak of successfully reaching base to 22 games. But senior Dustin Shirley, who belted a walk-off solo homer in the series opener for a 2-1 victory and had two singles in this game, hit a sharp grounder right at the shortstop for an inning-ending force at second.

After three scoreless innings from Vasquez (0-3), Dartmouth finally broke the deadlock in the 13th thanks to Sullivan’s heroics.

Dartmouth continues its quest to qualify for the Ivy League Championship Series when it hosts Princeton (10-23, 7-11 Ivy) for a three-game series this weekend. The doubleheader on Saturday will begin at 11:30 a.m. with Sunday’s finale set to start at 1 p.m. All three games will be streamed live on the Ivy League Network, now available on Apple TV, Roku and the ILN app for Android and Apple devices, with Wayne Young ’72 calling the action.

Notes: The last 13-inning game for Dartmouth was a 10-8 victory at Pacific on March 20, 2008 … the Big Green are now 1-1-1 in extra innings this year having lost and tied 11-inning games at Penn a month ago … Dartmouth is currently third in the Ivy League standings behind Yale (14-4) and Columbia (10-8) with two conference series remaining for the Big Green to just one for the other two. Only the top two teams advance to the ILCS, and not one team has secured a berth yet, though the Bulldogs would clinch home-field advantage with just one win at Penn on May 12-13.