Jordan Binnington stopped 38 shots, and the Blues withstood the emotional rush of Zdeno Chara's return to beat the Bruins 2-1 on Thursday night and take a 3-2 lead in the best-of-seven final. They can win the championship at home in Game 6 on Sunday night.
Ryan O'Reilly and David Perron scored for St. Louis, which has won two straight since a 7-2 loss at home in Game 3. It was the first time in the series a team has won two in a row.
Tuukka Rask stopped 19 shots and Jake DeBrusk scored for Boston.
O'Reilly scored in the opening minute of the second period, backhanding in a rebound for his third goal in his last five periods. It was still 1-0 midway through the third when the referees disregarded a leg sweep by Tyler Bozak that knocked Acciari out of the game. But he was still on the ice when Perron followed with a shot that banked off Rask's pad and into the net.
Boston cut the deficit to one goal on a delayed penalty with about 6 1/2 minutes left. Torey Krug took a high stick to the face at the blue line but he played on, straightened his helmet and dished the puck to DeBrusk for a one-timer past Binnington.
Boston pulled Rask with a little more than a minute left and earned several chances, but couldn't get the puck past Binnington.