Holtby finished with 44 saves as the Bruins outshot Washington 45-21, including 13-3 in the third period. The Capitals blocked another 26 shots, 12 in the third to hold the Bruins at bay.
The Bruins will head back to Boston for Game 5 on Saturday with this series knotted 2-2.
Third Period, 19:50, Capitals 2-1: The Bruins use their timeout with 9.5 seconds left and a huge faceoff to the right of Holtby. This could be the Bruins' last chance to tie this one.
Third Period, 18:50, Capitals 2-1: Thomas heads to the bench as the Bruins leave the net open for the extra attacker trying to get the equalizer.
Third Period, 15:35, Capitals 2-1: Milan Lucic with a steal, then sends a pass over to Krejci, but Krejci is nailed into the boards by John Erskine on one of the biggest hits of the night.
Third Period, 14:10, Capitals 2-1: Play is stopped as former Bruins defenseman Dennis Wideman goes down after taking a shot up high. He stays down briefly, but looks to be OK.
Third Period, 13:48, Capitals 2-1: The Bruins have more than doubled Washington in shots at 44-21, but it's the Capitals who have doubled up Boston on the scoreboard at this point thanks largely to a stellar game by the youngster in goal, Braden Holtby.
Third Period, 12:09, Capitals 2-1: The Bruins can't convert that power-play chance and still have not cashed in on a man-advantage opportunity in this series. The Bruins did not have a shot in that chance as the sides return to even strength.
Third Period, 10:09, Capitals 2-1: The Bruins will finally get their first power-play chance of the night as Johnny Boychuk draws the holding call on Mike Knuble after getting dragged down in deep behind the Washington net.
Third Period, 8:48, Capitals 2-1: The Bruins threaten again with Chara firing a shot in from the point with the fourth line providing traffic in front. Holtby snares it and prevents a rebound on Boston's 40th shot of the game.
Third Period, 7:22, Capitals 2-1: The Capitals with some sustained pressure for the first time in the third period, but Thomas is able to hold the fort against Washington's fourth line, stopping Keith Aucoin with Mike Knuble on the doorstop looking for a tip or rebound.
Third Period, 3:20, Capitals 2-1: The Bruins continue to pour pucks on Holtby. Boston has outshot Washington 6-0 in the third and 38-18 overall, but remain down a goal as the Capitals ice the puck to relieve the pressure.
Third Period, 1:28, Capitals 2-1: The Bruins dodge a bullet as Johnny Boychuk goes down to black a Jason Chimera shot on a 3-on-2 break that could have made this a two-goal game.
Third Period, 0:00, Capitals 2-1: The final frame is under way down there in Washington, where the Capitals are looking to close out a victory that would tie this series. Washington was 25-0-1 when leading after two periods in the regular season and is 1-0 with a lead after two in this series.
Second Intermission Notes: The Bruins will need a huge effort down in Washington to come home with a 3-1 series lead as the Capitals are 20 minutes away from tying the series after taking a 2-1 lead late in the second period.
Washington capitalized on its third power-play chance when Alexander Semin scored with 1:17 left in the period. The Bruins have not had a power play yet in this game.
The Capitals rallied late with a surge in the second half of the middle frame, but the Bruins still have a 32-18 edge in shots (18-15 in second), but Braden Holtby has come up huge in net for Washington. Tim Thomas hasn't been tested as often, but has come up with some big saves as well to keep the Bruins in striking distance.
The hits continue to come with frequency, with Washington holding a 29-24 edge there. Matt Hendricks leads the way with five, while Patrice Bergeron and Milan Lucic each have four for Boston, though Lucic did not record a hit in the second period. The Bruins also continue to struggle on faceoff, going just 20-33 (38 percent). Shawn Thornton is the only Bruin with a winning record at 1-0, while linemate Gregory Campbell is 3-10.
End Second Period, Capitals 2-1: The Capitals weathered the storm from the Bruins early, then struck on the power play late in the second to take a 2-1 lead into the final frame down in Washington.
Second Period, 18:43, Capitals 2-1: The Capitals convert this power-play chance, as Alexander Semin gives Washington the lead again.
He fired in a wrister from the left circle past Thomas to the high far corner.
Second Period, 17:53, 1-1: The Capitals will get another power play, then time with Patrice Bergeron going to the box for hooking after knocking the stick out of the hands of Brooks Laich.
Second Period, 15:31, 1-1: The Capitals are now leading in shots in the second period at 13-12. That after the Bruins opened the frame with a 10-2 edge, but thanks in part to a power-play chance, Washington has an 11-2 advantage since then.
Second Period, 14:08, 1-1: The Capitals continue to surge with a wild scramble in front of the Bruins net. Peverley then goes down to block a shot from the point and the Bruins are finally able to relieve the pressure.
Second Period, 11:45, 1-1: The Bruins kill off the penalty despite a ton of pressure from the Capitals, who put five shots on Thomas during the power play.
Second Period, 9:45, 1-1: The Capitals will now get another chance on the power play as Johnny Boychuk is sent to the box for hooking Troy Brouwer.
Second Period, 8:20, 1-1: The Capitals threaten and once again it's Brooks Laich with the chance, but this time he hits the crossbar as the Bruins dodge a bullet.
Second Period, 6:23, 1-1: The Bruins continue to dominate everywhere but on the scoreboard. The shots are 11-3 in the second and 25-6 overall, but it remains 1-1.
Second Period, 4:18, 1-1: The Bruins with some strong pressure from the Krejci line as Seguin, Marchand and Chara all have shots in a flurry in the Washington zone, but Holtby comes up huge.
Second Period, 1:15, 1-1: Thomas comes up with another big save on Laich, this time on a one-timer from the slot off a feed from Alexander Semin after a Johnny Boychuk turnover.
Second Period, 0:00, 1-1: The middle frame is under way down there in Washington, where the Bruins will look to build off a strong opening frame and try to cash in on more of the chances they're creating.
First Intermission Notes: The score is deadlocked 1-1, but the Bruins turned in arguably their best period of the series in the opening frame down there in Washington.
Boston kept the play in the Capitals zone for most of the period, outshooting Washington 14-3. The Capitals had just one shot for nearly 13 minutes, but that gave them a 1-0 lead for most of the period before Rich Peverley managed to tie it on an odd-man break.
Tim Thomas didn't have much work, but he bounced back from giving up a goal on the first shot he faced with a huge stop on Brooks Laich in front just before the Bruins tied it.
Unlike the games around the league Wednesday night, the referees are letting the teams play. There was just one penalty called, a slash on Peverley when he snapped Jay Beagle's stick. There hasn't been much rough stuff, but it has been physical, with the Caps holding a slim 15-14 edge in hits. Alex Ovechkin leads them with three, but Milan Lucic leads all players with four as he appears very motivated for this one.
The one area the Bruins need to improve is on draws. They were just 10-18 (36 percent) on faceoffs in the first, with Gregory Campbell 1-6.
End First Period, 1-1: The opening period comes to a close down in Washington, where the Bruins dominated play for most of the period and had a 14-3 edge in shots, but have to settle for a 1-1 tie on the scoreboard.
First Period, 19:22, 1-1: The Bruins kill off that penalty without allowing a shot. The teams return to even strength with Boston still up 14-2 in shots.
First Period, 17:22, 1-1: The Bruins take the first penalty of the night as Rich Peverley is called for slashing after snapping the stick of Jay Beagle.
First Period, 13:12, 1-1: The Bruins finally break through as Rich Peverley ties the game on an odd-man break.
Peverley leads a break with Gregory Campbell and Daniel Paille coming and only John Erskine back. Peverley fakes the pass and buries the shot from the right slot.
First Period, 12:39, Capitals 1-0: The Capitals finally get another shot and nearly score again, but Thomas makes the point-blank save on Laich in front.
First Period, 10:20, Capitals 1-0: The Capitals have still not had another shot since their goal. The Bruins lead 10-1 in shots more than halfway through the period but still trail 1-0 on the scoreboard.
First Period, 6:39, Capitals 1-0: The Bruins are lucky to avoid a penalty as Benoit Pouliot catches Mike Green across the face with a high-stick but no call is made.
First Period, 6:05, Capitals 1-0: The Bruins are dominating everywhere but the scoreboard as they continue to pressure Holtby. The shots are 9-1 Boston, but the Capitals converted their only bid on Thomas for the one-goal lead.
First Period, 4:52, Capitals 1-0: The Bruins try to answer back with some pressure in front, but Holtby is up to the task, stopping Lucic on a rebound in front among the chances Boston created.
First Period, 1:22, Capitals 1-0: The Capitals strike first as Marcus Johansson finishes a 2-on-1 chance from the right wing.
The Caps broke in for the odd-man rush after Andrew Ference went down in a collision with Alex Ovechkin in the neutral zone. Brooks Laich carried it down the left wing and crossed it to Johansson for the goal.
First Period, 0:00, 0-0: They are under way down in Washington, where the Bruins will try to take control of this series with a victory for a 3-1 lead before returning home and the Capitals will look to pull even at 2-2 on home ice.
7:30 p.m.: The Bruins will open with Milan Lucic, Patrice Bergeron and Rich Peverley up front, Dennis Seidenberg and Johnny Boychuk on defense and Tim Thomas in goal.
The Capitals counter with Matt Hendricks, Jay Beagle and Troy Brouwer up front, Karl Alzner and John Carlson on the blue line and Braden Holtby in net.
7:25 p.m.: No changes in the Bruins scratches, with Jordan Caron, Mike Mottau, Adam McQuaid (upper body) and Tuukka Rask (groin) out again.
Mike Knuble and John Erskine are in for Washington, which scratches Jeff Schultz, Jeff Halpern, Dmitry Orlov, Mattias Sjogren, Tomas Vokoun (groin), Michal Neuvirth (leg) and Nicklas Baclstrom 9suspension).
7:15 p.m.: Based on reports out of Washington, the Bruins used the same line combinations in warm-ups that they deployed in Game 3.
That leaves Patrice Bergeron between Milan Lucic and Rich Peverley and David Krejci with Brad Marchand and Tyler Seguin. The Benoit Pouliot-Chris Kelly-Brian Rolston and Daniel Paille-Gregory Campbell-Shawn Thornton combinations remain intact.
7 p.m.: No surprises in the warm-ups, with reports out of Washington from those on the scene noting that Tim Thomas and Braden Holtby led the teams out and will be the starters in goal.
Mike Knuble and John Erskine were both spotted on the ice for Washington. Knuble will play his first game of the series with Nicklas Backstrom suspended, while Erskine will add some muscle to the blue line.
6:30 p.m.: After a two-day break, the Bruins return to action in a about an hour when they take on the Capitals down in Washington for Game 4 of their opening-round series.
The Bruins can take a commanding 3-1 lead with a win, but the Capitals can make it a whole new series with a Washington victory evening the series at 2-2.
8 a.m. ET: The Bruins have a chance to take a commanding lead in their Eastern Conference quarterfinal series when they take on the Capitals in Game 4 in Washington on Thursday.
A win will give the Bruins a 3-1 lead in the series and a chance to close it out on home ice back in Boston in Game 5 on Saturday. But if the Capitals can take advantage of their home ice on Thursday, the Bruins could be returning to the Garden with the series tied at 2-2 and facing a protracted struggle to get out of the opening round.
Everything in this series has been fiercely contested and close, with the Bruins needing overtime to win 1-0 in Game 1 and the Capitals prevailing 2-1 in double overtime in Game 2. Game 3 on Monday finally saw a game ended in regulation, but there was still plenty of drama with Zdeno Chara scoring the game-winner with just 1:53 left in regulation for a 4-3 victory.
The Bruins doubled their goal output from the first two games in Game 3, but still have not gotten any production out of their top two lines. Claude Julien switched centers Patrice Bergeron and David Krejci on Monday, with Bergeron moving up between Milan Lucic and Rich Peverley and Krejci sliding in between Brad Marchand and Tyler Seguin. That didn't produce any results (Boston got its goals from the third and fourth lines and two while playing 4 on 4), but he stuck with the change in practice on Wednesday and appears ready to try it again in Game 4.
Washington will also have to switch up its top lines as Nicklas Backstrom is suspended for Game 4 after cross-checking Peverley in the face at the end of Monday's game. Mathieu Perreault is expected to move up into Backstrom's spot between Jason Chimera and Alexander Semin, while former Bruin Mike Knuble will likely return to the lineup after being a healthy scratch for the first three games.
The puck drops at 7:30 p.m. Tune in to NESN to watch the game, and stay with the NESN.com live blog, as we'll keep you up to speed on everything happening.
