Nicklas Backstrom gave the puck away on a pass that ended up with Boston's David Krejci. Krejci passed it forward to Milan Lucic, who gave Seguin the puck with an opportunity to score one-on-one against Braden Holtby. Holtby came out to contest the shot and Seguin remained patient, held on, and took an easy shot at an open net after sliding past the goalie.
Here's video of Seguin's game-winner:
This Caps fan really says it all:
This has been an exciting series, to say the least: After six games, each side has scored the exact same number of goals. That won't remain true, as one side will pull ahead by winning Game 7, and the series.