The Caps kept the heat on in the attack zone for another minute or so but faded out offensively thereafter at 5-on-5.
Early in the second, the Caps found themselves in some penalty-killing peril, dealing with a two-man advantage for the Bruins for a span of 58 seconds. About a minute after they successfully navigated their way through that stretch, they went on a man advantage of their own.
After a successful entry into Boston ice, Vrana fed Carlson at center point. Carlson crept down to the high slot and put a wrist shot bar down behind Halak to make it a 3-0 game at 8:35.
Boston broke through four minutes later, getting on the board after winning an offensive-zone draw. David Pastrnak had enough time and space to pull the trigger twice from the high slot after the B's won the face-off, and the second one beat Vitek Vanecek at 12:37 to make it 3-1.
Pastrnak struck again to make it a 3-2 game at 6:08, scoring seven seconds after a Boston face-off win in Washington ice. Carlson wiped out behind the Washington net on the play, giving the B's a de facto 5-on-4 in front. For the second time in as many goals, the dangerous Pastrnak had way too much room with which to work.
A couple minutes later, Boston forward Trent Frederic challenged Washington's Tom Wilson to a bout, one that the Caps winger probably should have turned down. Wilson was one of the Caps' best and most consistent players on this night, and losing him for five minutes with 11:11 left in a one-goal game did Washington no favors.
Alex Ovechkin failed to clear the zone and ended up taking a slashing penalty to compound his initial mistake. Washington killed that minor - its penalty-killing outfit had a strong night - but the Bruins tied the game before Wilson and Frederic exited the box.
Boston defenseman Jeremy Lauzon made a strong play, carrying down the right side and issuing a perfect backhand feed for a wide-open Craig Smith, who beat Vanecek with a one-timer from the bottom of the left circle to tie it at 13:07.
The Bruins kept the heat on and took the lead on a goal from their fourth line a little over four minutes later. Boston winger Sean Kuraly collided with Conor Sheary high in Washington ice. As Sheary slowly tried to hobble off in obvious discomfort, Boston won a puck battle on the left half wall, and Kuraly was able to feed Brandon Carlo for the go-ahead goal on a one-timer from in tight with 2:37 left. It was a great shot, but once again, the B's had a de facto 5-on-4 in this situation, as Carlo was open because he was Sheary's guy.
Marchand's empty-netter ended whatever drama may have remained.