In the extra period, Buchnevich was alone at the right corner when he took a pass from Robert Thomas and slammed the puck past Thompson.
The game opened with a battle between goaltenders, as Binnington and Thompson were exceptional at keeping the puck out of the goal.
After a relatively quiet first period, Toropchenko deflected a shot from Colton Parayko and past Thompson to give the Blues a 1-0 lead with 21 seconds left.
Binnington continued to stymie Vegas’ efforts in the second period, exemplified by three highlight saves.
The third might have been the most impressive, with 2:30 left in the second, when Barbashev swiped the puck at the blue line and sprung Eichel for a chance in front only to have Binnington poke-check the puck off his stick at the doorstep.
The Golden Knights finally broke through when Eichel fired a shot from the top of the right circle and it found its way past Binnington into the top-left corner for a power-play goal with 7:02 left in regulation.
Vegas had failed on its first three power-play opportunities. The Blues came into the game with the league’s second-best road penalty kill having stopped 28 of 31 shots (90.3%).
The teams conclude a home-and-home series in St. Louis on Wednesday.
AP NHL: https://apnews.com/hub/NHL
W.g. Ramirez, The Associated Press