After clanging the potential winner off the post in the final two minutes of regulation, Carl Gunnarsson scored on a delayed penalty 3:51 into overtime to give St. Louis a 3-2 victory over the Boston Bruins and tie the Stanley Cup Final at a game apiece.
Jordan Binnington made 21 saves, and Robert Bortuzzo and Vladimir Tarasenko scored in regulation to send a game in the championship series to overtime for the first time since 2016.
It was the Blues' first victory in the Stanley Cup Final in franchise history after 13 straight losses.
Charlie Coyle and Joakim Nordstrom scored and Tuukka Rask made 33 saves for Boston, which won 4-2 in Game 1 on Monday night for their eighth straight postseason victory.
Gunnarsson also assisted on Bortuzzo's first-period goal and then hit the post behind Rask with about 2 minutes left in regulation. In the final minute, Boston's David Pastrnak had a chance off a faceoff, but Binnington turned it away.
After a furious first period that ended in a 2-all tie, the teams went on defense in the second. Despite four penalties, including a high-sticking, blood-drawing double-minor against Boston's Connor Clifton, neither team was able to score.
It stayed tied through a hard-hitting third period, with both teams failing to convert good scoring chances and avoid overtime.
But after the break, it was all Blues.
Boston did not get off a shot in the overtime, and the Eastern Conference champs struggled to clear it out of their own zone. Alexander Steen drew a hooking penalty in front of the net, and the Blues pulled Binnington for an extra skater.
Gunnarsson worked it around to the blue line, passed it to Oskar Sundqvist and then got it back for a rifle shot over Rask's stick side into the corner of the net.
Game 3 is Saturday night in St. Louis.