Tempers flared after the goal with an incensed Chara going after Pacioretty, then Hal Gill and Scott Gomez, though the scrum never developed into any actual fights.
The Bruins lost when leading after two periods for the first time this season, as Montreal outshot them 18-8 in the third and 5-0 in OT for a 42-29 overall advantage. The Bruins technically stay in first place in the Northeast Division as they earn a point for the OT loss. Boston and Montreal are tied with 49 points, but the Bruins stay in first because they have two games in hand on the Habs.
It won't get any easier for the Bruins, who will have to try to bounce back from this devastating defeat when they take on the Penguins in Pittsburgh on Monday.
Overtime, 2:10, 2-2: The Bruins survive that power play and live on to try to get the second point in this one.
Overtime, 0:10, 2-2: The five-minute overtime is under way and 10 seconds in Blake Wheeler takes a bad hooking penalty on Wisniewski deep in the Montreal end to give the Habs a 4-on-3 power play.
End Regulation, 2-2: This one won't be settled in 60 minutes, as the Bruins can't hold their late lead and Montreal forces overtime.
Third Period, 19:12, 2-2: The Habs have come all the way back, as James Wisniewski fakes a shot from the blue line, then flips it in with Brian Gionta crashing the crease in front of Thomas for the deflection.
After a review, the goal stands and this one is tied.
Third Period, 18:54, Bruins 2-1: The Bruins nearly end this one, but Chara's long clear dribbles just wide of the empty net, giving the Habs a faceoff in the Boston zone with an icing.
Third Period, 17:38, Bruins 2-1: This one isn't over yet, as Montreal converts on the power play with a goal by Scott Gomez to cut the lead to one.
Gomez sent it in from the left boards and it appeared to change direction slightly as it tipped off Chara's skate and slipped between Thomas' legs.
Third Period, 16:32, Bruins 2-0: Huge penalty kill coming up here for the Bruins, as Ryder takes a bad tripping penalty after upending James Wisniewski at the Montreal blue line.
Third Period, 14:23, Bruins 2-0: Wheeler steals an attempted clear by Price, but Price gets back in time to block Wheeler's shot on goal.
Third Period, 12:28, Bruins 2-0: The fourth line finally provides some pressure for the Bruins, with Paille shooting wide off a feed from Thornton and Campbell stuffed on a wraparound attempt.
Third Period, 11:41, Bruins 2-0: The Habs continue to press, but Thomas has been up to the task so far. Montreal is outshooting Boston 9-4 in the third.
Third Period, 9:50, Bruins 2-0: Thomas is under siege here, as the Canadiens pepper him with shots and the Bruins struggle to clear the puck.
Third Period, 7:57, Bruins 2-0: The video review upheld the no-goal call for the puck being batted in with a high stick, so the Bruins retain their two-goal lead.
Third Period, 7:57, Bruins 2-0: The Habs finally get one past Thomas when Darche bats it out of midair on a rebound at the top of the crease, but after some initial confusion, the refs ruled it no goal on the ice. The play is under review.
Third Period, 5:26, Bruins 2-0: Thomas makes his biggest saves of the night as he stops Mathieu Darche's shot from the slot, then Benoit Pouliot's rebound at the right post.
Third Period, 4:35, Bruins 2-0: The Bruins come up empty once again on the power play, and Plekanec actually had the best scoring chance shorthanded for Montreal, but Thomas made the save.
Third Period, 2:35, Bruins 2-0: The Bruins have a chance to extend the lead with another power play as Jeff Halpern gets called for hooking as he takes Boychuk awkwardly into the boards in the corner.
Boychuk was slow getting up but appeared OK.
Third Period, 0:00, Bruins 2-0: The final frame is under way in Montreal, where the Bruins will look to hold on to this two-goal lead, and extend their one-point lead in the division.
The Bruins are 16-0-0 when leading after two periods this year, while Montreal is 0-15-1 when trailing after two.
Second Intermission Notes: The Bruins, and especially Patrice Bergeron, put together a strong second period to take a 2-0 lead after 40 minutes.
Bergeron had both goals on two shots in 12:04, as the reunited line of Bergeron, Mark Recchi and Brad Marchand has clicked nicely.
The Bruins outshot the Habs 10-7 in the second (21-19 overall) and also did a better job on faceoffs. They still are just 19-26 (42 percent) overall, but went 13-11 in the second. Greg Campbell has led the way, going 7-2 so far.
Montreal will have to try to come back without Michael Cammalleri, who will not return to this game after suffering an undisclosed injury.
End Second Period, Bruins 2-0: The middle frame comes to a close with the Bruins taking a two-goal lead thanks to a pair of goals by Patrice Bergeron.
Second Period, 18:41, Bruins 2-0: The Bruins have a chance to extend the lead further with a 2 on 1 with Lucic and Ryder. Lucic sent the puck over to Ryder on the right side, but his shot sailed high.
Second Period, 17:30, Bruins 2-0: The Bruins successfully kill off that penalty.
Boychuk did not miss a shift as he was right back out there on the PK.
Second Period, 15:30, Bruins 2-0: The Bruins will be on the penalty kill for the first time in this one, as Blake Wheeler is sent off for hooking.
The worse news might be the status of Johnny Boychuk, who limped off in pain after blocking a shot.
Second Period, 12:27, Bruins 2-0: The Bruins double the lead as Patrice Bergeron scores his second of the night to finish a great shift from that line.
Mark Recchi, Brad Marchand and Bergeron kept the Habs hemmed in the zone and Bergeron finally put the puck home from the top of the right crease, sliding it inside the far post. Chara picks up the lone assist, but strong work by Recchi and Marchand to help create that chance.
Second Period, 10:20, Bruins 1-0: Rough shift for Savard, as he gets tossed from the faceoff, then tries to drop a fancy no-look pass between his legs that goes to no one and sails out of the zone.
Second Period, 7:40, Bruins 1-0: Ryder tries to set up Savard in front, but Moen breaks it up on the backcheck.
Second Period, 6:30, Bruins 1-0: Shawn Thornton with some words for P.K. Subban, but the Habs' brash youngster wants nothing to do with the Boston tough guy.
Second Period, 4:18, Bruins 1-0: The Bruins finally take a lead on the Habs as Patrice Bergeron opens the scoring by completing a slick passing play.
Brad Marchand started it by taking a hit to make a play, getting the puck over to Blake Wheeler in the left circle, and Wheeler one-touched a pass to Bergeron at the right post for the goal.
Second Period, 3:18, 0-0: The Bruins had better movement in that power play, creating a couple decent chances. But Boston still goes to 0 for 12 on the man-advantage in the last five games.
Second Period, 1:18, 0-0: The Bruins will get another chance on the power play as Plekanec goes to the box for the second time, this penalty for slashing after knocking the stick out of Steven Kampfer's hands.
Second Period, 0:29, 0-0: The Bruins come within inches of getting that first goal, as Bergeron clangs one off the near right post from the high slot off a nice feed from Marchand.
Second Period, 0:00, 0-0: The middle frame is under way, with the Bruins and Habs still looking for the first goal in this one.
First Intermission Notes: The Bruins played a solid road period to start this one. They weren't able to score, but they created some chances and kept Montreal off the board as well.
Tim Thomas showed no signs of rust in his first start on 2011, as he stopped all 12 shots he faced. Carey Price was equally strong at the other end with 11 saves.
Two areas do need improvement though. Boston was horrible in the faceoff circle, going just 6-15 (29 percent). Usual stalwart Patrice Bergeron was 2-6, while Marc Savard and David Krejci were each 1-4.
The other area of concern is the power play, which failed to produce even a single shot on goal on Boston's first opportunity. The Bruins are now 0 for 11 over their last five games and have not scored a power-play goal since Mark Recchi's last-minute game-winner in Tampa Bay back on Dec. 28.
End First Period, 0-0: The opening period comes to a close in a scoreless draw as the old rivals felt each other out a bit in that opening 20 minutes, but neither team was able to get on the board.
First Period, 18:47, 0-0: Thomas makes a save in a scramble in front, and the shoving leads to a full-fledged fight with Adam McQuaid and Travis Moen dropping the gloves.
It was a long bout with Moen landing some rights early, but McQuaid getting the better of the shots, particularly with some left jabs, as the battle wore on.
First Period, 16:05, 0-0: The Habs answer with a bid of their own as Michael Cammalleri launches a bomb from the right side after a Bruins turnover, but Thomas makes the stop.
First Period, 14:51, 0-0: The Bruins with another bid from a defenseman, this time with Chara stepping up for a one-timer from the point that Price turns aside.
First Period, 12:57, 0-0: The Bruins with some nice pressure from the top line. Lucic finds Ryder with a long crossing pass, and Ryder drops it back for a one-timer by kampfer, who once again joins the attack to create a scoring chance.
First Period, 9:44, 0-0: The Bruins are having trouble containing Montreal's speed, which has led to a few chances for the Habs. Marchand answered with Boston's best bid in a while with a shot from the slot off a feed by Krejci.
First Period, 7:03, 0-0: The Bruins, who were 0 for 4 on the power play on Thursday, don't start this night any better with little pressure on that man-advantage.
First Period, 5:03, 0-0: The Bruins get the first power-play chance of the night as Tomas Plekanec is called for hooking.
First Period, 3:51, 0-0: Johnny Boychuk almost with a costly giveaway in his own zone, but Patrice Bergeron is able to steal it back before the Habs could cash in on the chance.
First Period, 3:00, 0-0: Chara getting his usual treatment in Montreal, with the Habs fans booing him every time he touches the puck.
First Period, 1:40, 0-0: Thomas, making his first start in four games, shakes off the rust quickly as he gets an early test on a shot from the slot by Brian Gionta, but Thomas makes the save.
First Period, 0:00, 0-0: And they're under way at the Bell Centre, with first place in the Northeast Division at stake as the Bruins and Canadiens clash for the 708th time in the regular season.
7 p.m.: The official scratches are in, with Nathan Horton (undisclosed) and Mark Stuart (hand) out for Boston.
Defenseman Yannick Weber and forward Lars Eller are the scratches for Montreal, which will start Benoit Pouliot, David Desharnais and Mathieu Darche up front, Alexandre Picard and James Wisniewski on defense and Carey Price in goal.
The Bruins will counter with Brad Marchand, Patrice Bergeron and Mark Recchi up front, Zdeno Chara and Steven Kampfer on the blue line and Tim Thomas in goal.
6:45 p.m.: Nathan Horton did not skate in warm-ups and it appears he will indeed miss his first game as a Bruin with an undisclosed injury.
With Horton out, there will be even more shuffling of the lines than planned. The new combinations set to start this one appear to be:
That moves Marchand back up to a scoring line. Seguin shifts back to wing, but on a new line with Krejci and Wheeler, while Paille gets back into the lineup. Only the Lucic-Savard-Ryder combo remains from how the Bruins lined up in practice on Friday.
6:30 p.m.: Tim Thomas and Carey Price did lead their respective clubs onto the ice for warm-ups, confirming that will indeed be the goaltending matchup in this one.
6 p.m.: The Bruins and Canadiens will renew their ancient rivalry in just about an hour, but the Bruins will likely be doing it without Nathan Horton.
Claude Julien stated that the forward was "very unlikely to play" in this one after leaving practice early on Friday with what the team would reveal only as some "discomfort."
Tim Thomas and Carey Price were the first goalies off the ice at the morning skate, so that should be the goaltending matchup in this one.
8 a.m.: After a disappointing return home for a 3-1 loss to Minnesota on Thursday, the Bruins head back out on the road for short but pivotal trip.
Boston's first stop is in Montreal on Saturday, where the Bruins and Canadiens will clash in a showdown for first place in the Northeast Division. The Bruins have another big challenge in store with a trip to Pittsburgh on Monday before returning home, but they won't worry about that one until after they've dealt with the hated Habs at the Bell Centre.
"It's very exciting," Bruins forward Brad Marchand said. "We've battled with them for a while now, and obviously it's been a huge rivalry for about a hundred years now, so it's going to be a lot of fun.
"It's one of those games where there's no place else you'd rather be," Marchand added. "It's going to be a battle, but it's going to be a lot of fun. It's going to be a great atmosphere up there."
With Montreal beating Pittsburgh 2-1 in a shootout on Thursday coupled with the Bruins' loss to the Wild, Boston comes into this one with just a one-point lead on Montreal in the division. The Bruins are currently third in the East thanks to their division lead, but could fall to the eighth and final playoff spot with a loss.
"We know it's us or them right now, they're chasing us for that third spot [in the East]," Bruins center Marc Savard said. "They're a point behind now after last night. We have games in hand but these [head-to-head matchups] are the ones that really count so we have to go up there, have a good start and go from there."
How Savard responds to the giveaway he led to Minnesota's game-winning goal and a third-period benching on Thursday will be one of the main things to watch in this one.
Bruins coach Claude Julien shook up the lines in practice on Friday, moving Nathan Horton down with David Krejci and Blake Wheeler and Michael Ryder up alongside Savard and Milan Lucic. But those plans may have to be altered as Horton left practice early with what Julien termed some "discomfort" and his status for this game is questionable.
The Bruins have already lost to Montreal in each of the first two meetings this year, falling 3-1 at home on Nov. 11 and 4-3 in Montreal on Dec. 16. But the Bruins welcome the challenge of taking on the Habs again.
"Personally I like those kind of games," Julien said. "There's a lot at stake. Those are the kind of games you thrive for. You want those games to have meaning and you always want to make sure you come out on top."
The puck drops at 7 p.m., so check back here throughout the day for updates on all the action.