Souray's blast off a feed from Plekanec 2:01 into overtime lifted the Canadiens to a 4-3 NHL victory on Sunday afternoon and ended the Pittsburgh Penguins' six-game winning streak.
"Someone poke-checked (Sidney) Crosby and I just raced up ice as quickly as I could," Souray said of his team-leading 18th goal of the season. "Tomas put it right on my stick.
"It was a big win. We needed these points."
Plekanec, Montreal's hottest scorer, also had two goals and Mark Streit had another as the Canadiens (29-19-6) moved one point ahead of Ottawa into fourth place in the Eastern Conference, each with 54 games played.
League scoring leader Crosby set up goals by Jordan Staal and Ryan Whitney, while Michel Ouellet scored the tying goal that forced overtime with 2:34 left in the final period for Pittsburgh (26-18-8).
Despite the loss, the red-hot Penguins extended their string of games with at least one point to 10.
The sell-out crowd of 21,273 was on Crosby's back for most of the game and after he went down in the third period from what may have been a high stick but wasn't called, the crowd chanted "faker, faker."
The Penguins had beaten Montreal 5-4 in a shootout in an emotional and at times nasty match in Pittsburgh last week, but the only incident of note in this one was a jawing match on the benches between Crosby and Montreal enforcer Aaron Downey.
"It's a road game," Crosby said with a shrug. "I grew up liking this team (Montreal) and there's a reason they're passionate fans. My liking this team has probably changed since then."
What marked the rematch was that Montreal was slapped with eight minor penalties, including the first six of the game, while Pittsburgh took only two, scoring on both while the Pens went three-for-eight.
"It was unbelievable," Streit said. "Even in the third period, I was thinking we never have a power play. We're always short.
"It was a different game, but it was important for us and it was pretty spectacular at the end. And we did it."
Montreal trailed 2-1 going into the third period and now lead the league in wins when behind after two frames with seven, one more than Detroit.
It was Plekanec who stripped the puck from Crosby inside the Montreal blue-line to set up the two-on-one that produced Souray's game-winner. Plekanec has five goals in the last seven games, while Streit has three in his last four.
"It's part of the learning process," coach Michel Therrien said of Crosby's turnover. "I'm OK with it, as long as we don't keep repeating the same mistake.
"He's not the type that will end up losing the puck (often). He's pretty strong on the puck. We leave this building with one point and I thought we played a decent game. They made some comments after the last game that they were waiting for us, but we were there and we played. For a young team, we showed a lot of character."
Montreal was coming off a 4-2 loss at home Saturday afternoon to the New York Islanders and angry coach Guy Carbonneau made changes, scratching struggling wingers Sergei Samsonov and Alexander Perezhogin.
He also put captain Saku Koivu on a line with checkers Streit and Mike Johnson, going head-to-head with Crosby, and he dumped Michael Ryder to the fourth line.
"Chris Higgins and Ryder have struggled lately so we thought we'd make a change," said Carbonneau. "We also wanted someone to play against Crosby, so we put (Koivu) with Johnson and Streit.
"It was a big team win."
It went fine early, but the Canadiens encountered penalty trouble and Staal opened the scoring during a two-man advantage at 11:33. Montreal was handed the first six minors of the game.
David Aebischer then kept the home side in the game, making a smart glove save on Ouellet from the doorstep and seeing Crosby miss a wide-open net.
Plekanec beat Mark Eaton to Maxim Lapierre's rebound to tie the game 4:48 into the second frame, but Crosby faked a shot and slid the puck for Whitney to fire into an open side on a power play only 47 seconds later.
The crowd booed the Canadiens off the ice at the end of the second period, but Eaton was sent off 49 seconds into the third period and Plekanec then banged in Alex Kovalev's rebound to tie the match again.
Pittsburgh's second minor went to Evgeni Malkin, and this time Streit went to the net to jam Ryder's rebound in.
On Tuesday, Montreal remains at home to face Carolina while the Penguins return home to play Nashville.
The Canadiens began playing two afternoon games on Super Bowl weekend in 1990-91 and are 17-11-4 in those games.
Notes - Andrei Markov, Montreal's best defenceman for most of the season, sat out with a "lower body" injury. . . Little-used defenceman Janne Niinimaa and enforcer Aaron Downey were dressed. . . The Pens' Colby Armstrong, who injured a knee Thursday against Montreal, sat out a second game.