The Presidents' Trophy winners and defending Eastern Conference champions can advance with a win against Detroit on Saturday at home.
Torey Krug scored midway through the second period to pull the Bruins to within a goal. Milan Lucic tied it at 2-2 early in the third period.
at Minnesota 2, Colorado 1: Charlie Coyle scored his third goal of the series for Minnesota, and the Wild dominated the Avalanche for the second straight game on their way to a victory that evened the first-round matchup at two apiece.
The Wild outshot the Avalanche a stunning 32-12, establishing a franchise record for fewest allowed by Minnesota.
Jared Spurgeon used a slap shot to get a puck past Colorado's Semyon Varlamov just 3:47 into the game, much quicker than the 65:08 the Wild needed to score the last time.
Game 5 will be in Denver on Saturday night.