Following the negated Acciari tally, the game remained scoreless until the 5:49 mark of the third period. That's when Erik Karlsson and Bobby Ryan - two players who have given the Bruins fits in this series - hooked up for the game's lone goal.
Karlsson corralled the puck at the point and sent a slap pass to Ryan at the left post. A sprawling Tuukka Rask (26 saves) stopped Ryan's first attempt, but his second try squeaked over the goal line to give Ottawa a 1-0 lead they would not relinquish.
"I think it hit somebody's skate. I didn't see [Karlsson] releasing that puck, but I think it hit a skate and just [went] to the back door," said Rask. "I had my stick on it, and I just couldn't pull it back, and then [Ryan] had an extra second and just stuffed it in."
Ryan (three goals, two assists) and Karlsson (five assists) are pacing the Senators with five points apiece in the series.
"A night like tonight, I thought we defended fairly well," said Bruins interim head coach Bruce Cassidy. "Karlsson, he popped out of nowhere. We know that. We've identified that he's their best player, but that doesn't mean he's not going to get his opportunities...their goal, obviously, we weren't good enough in D-zone. We had a missed assignment and they out willed us at the night.
"You've got to give him credit. He's a good player, Bobby Ryan. We've seen that in this series. He's a big body and that ends up being the difference in the game."
The Bruins, meanwhile, managed just five shots in the third period. But while the opportunities were limited, they felt the chances they did get were good ones.
"I thought we did a pretty good job down there," Brad Marchand said of the team's play in front of Ottawa's net. "We had a lot of really good opportunities and their goalie made some big saves, so you've got to give him credit. He's a good goalie."