Dennis Wideman scored the first goal of the evening with 12:01 left in regulation, one-timing a shot past Tim Thomas from the high slot to give Washington a 1-0 lead. Marcus Johansson doubled the advantage 1:55 later, finishing off a 2-on-1 break with Alex Ovechkin to make the score 2-0.
But the Bruins were able to rally in the final moments. David Krejci deflected a Zdeno Chara point shot past Michal Neuvirth to cut the deficit to 2-1 with 3:10 to go. Then, after the Capitals failed to clear the zone, Andrew Ference's shot fluttered past Neuvirth to tie the game, 2-2 with 1:16 to go.
After a frantic overtime period, the Capitals claimed the extra point in a shootout. The Bruins led 2-1 with one shooter still scheduled, but Alexander Semin lifted a backhand past Thomas to tie the shootout count, 2-2. After Neuvirth stopped Rich Peverley, Brooks Laich finished the evening by lifting another backhander over Thomas.
The Capitals are now tied with the Sabres for the eighth and final playoff spot in the Eastern Conference, though Washington has played one more game. Buffalo hosts the Pittsburgh Penguins Friday night.