* Holtby shines with 44 saves
* Series heads back to Boston for game five
* Semin scores the game winner (updates with quotes, details)
The Washington Capitals overcame the absence of Nicklas Backstrom and a 45-21 disadvantage in shots on goal to defeat the Boston Bruins 2-1 on Thursday and level their Eastern Conference first round playoff best-of-seven series at 2-2.
Braden Holtby, the Capitals' 22-year-old rookie netminder, was brilliant in goal, repeatedly stopping Boston drives to the net with acrobatic saves.
With Washington clinging to a 2-1 lead, the Bruins outshot the Capitals 13-3 in the final period but could not get past Holtby, who was summoned from the minors late in the season because of injuries to the club's top two netminders.
"Holts was very good," said Capitals coach Dale Hunter, whose team have killed off all 12 penalties in the series. "He stood tall and kicked out a lot of rubber tonight."
Boston's Rich Peverley tipped his hat to Holtby's 44-save performance but said his team needed to hang around the net a bit more to take advantage of loose pucks.
"We can get better net presence," Peverley said. "They buried their chances. We had a few that kind of rolled off to the side and we weren't there to bang the puck in.
"We're going to have to do that to win."
The series, with each game having been decided by just one goal, heads back to Boston for Game Five on Saturday.
Washington scored the game-winner with 1:17 left in the second period when Alexander Semin blasted a shot from the left wing circle past Boston's stunned netminder Tim Thomas.
"He's got great skill," Hunter said of Semin. "They left him open for a second. With his wrist shot, it was a laser, right in the corner. Great shot. Thomas didn't have a chance."
Semin's goal gave Washington a 2-1 lead and Holtby ensured the Capitals preserved the lead.
"All of the guys right now feel excited about the series," said Washington's two-time NHL MVP Alex Ovechkin.
"I always said after the first game (a 1-0 Boston win) it's going to be a long series and you never know what's going to happen.
"Step by step, game by game we're going to take it and try to win this series."
Washington set the tone just 1:22 into the game when Marcus Johansson flicked a wrist shot into the net, beating Thomas high to the glove side for his first goal of the series.
The goal ignited the crowd of nearly 19,000 and vanquished any fears the Capitals would suffer any fallout from the loss of Backstrom, who was suspended for cross-checking Peverley in the face at the end of Boston's 4-3 victory on Monday.
Peverley tied the score at 1-1 with less than seven minutes left in the opening period when he fired the puck from the right wing circle through the legs of Holtby, but that was the end of their highlights.
"We tied the game. We were right back where we wanted to be," said Boston head coach Claude Julien. "But at the end of the night the result wasn't the one we wanted.
"When you shoot 40 shots on net you would expect your team to get more than one goal."