The Bruins are a win away from advancing to the second round of the Stanley Cup Playoffs.
Brad Marchand snapped a 1-1 tie late in the second period and the Bruins went on to beat the Maple Leafs 3-1 in Game Four of their Eastern Conference quarterfinal in Toronto.
Torey Krug scored in the first and Jake DeBrusk added an insurance marker early in the third for Boston, which leads the best-of-seven matchup three-games-to-one.
Tomas Plekanec had the lone Toronto goal in the first.
Patrice Bergeron, part of a top line that combined for 20 points in the Bruins' two emphatic home victories to open the series, was a surprise late scratch with an upper-body injury. Riley Nash took his spot between Marchand and David Pastrnak.
The Bruins host Game Five on Saturday.