The veteran centre scored with 1:07 left in the third period to break a tie and then added an empty-net goal to give the Canadiens a 5-3 victory over the Columbus Blue Jackets on Thursday night.
Montreal had blown a 3-0 lead and was having all they could handle in holding off the Jackets' young forwards when Plekanec came over the blue-line and fooled goalie Sergei Bobrovsky by taking a quick shot along the ice instead of passing off to open winger Brandon Prust.
The puck went in off the goalpost to give Montreal (5-2-0) its fourth straight win.
"I tried a no-look shot on the goalie," said Plekanec, who had been off to a slow start with only one goal in his first six games. "I had Prust on the left side, but I wanted to make sure I didn't make a turnover, so I put it on the net. I kind of got lucky."
The Blue Jackets got a power play in the final minute, but Plekanec was sent in alone by Prust for the empty netter with 16 seconds remaining. It was Montreal's second short-handed goal of the game.
"It's great, especially after a slow start for myself and our line," he said.
Michael Bournival got his first NHL goal and Rene Bourque also scored for Montreal, while defenceman P.K. Subban had two assists for 10 points in his last six games.
Rookie Boone Jenner scored his first two NHL goals and Ryan Johansen got his first of the season for Columbus (2-4-0), which has lost three in a row.
Jenner got both his goals by going to the net to pick up rebounds on power plays.
The first came during the same Columbus man advantage that Markov scored a short-handed goal on at 6:52 of the second frame to put the Canadiens up by three goals.
"It was pretty special," said Jenner. "And we got some momentum off of it, so it was good.
"It's a pretty cool building to get it in, obviously. I watched the Habs a lot growing up in Ontario. So it's kind of cool. It's one I'll remember for sure."
A Columbus lineup missing Marian Gaborik (flu) and Nathan Horton (shoulder) played with energy even after going down 2-0 in the first period, and made it a gripping, end to end contest for the 21,273 Bell Centre fans.
"We're a team that never quits," said 20-year-old Jenner. "We're not going to change our game no matter what the score is. We were down 3-0 and we started to pick it up. Getting a couple of power plays got us rolling a bit."
Montreal coach Michel Therrien called it the kind of game that fans love but that gives coaches grey hair. Montreal had a 36-33 shot advantage.
Therrien was concerned his team would come out flat in its first game at home after a four-game trip to western Canada but, led by Subban, they burst out of the gate.
Bourque, who has also been battling the flu, was alone at the far blue-line during a power play for a long pass up the middle from Subban that turned into a breakaway goal only 4:38 into the game.
Subban drew two opponents away to get the puck to Andrei Markov for a clever cross-ice pass that Bournival didn't get all of, but the captain of the 2012 Memorial Cup champion Shawinigan Cataractes saw it slide through Bobrovsky's pads at 12:01 of the first.
Markov made it 3-0 with a short-handed goal as his weak shot from the point went off a stick and past Bobrovsky 6:52 into the second frame.
Columbus struck back on the same power play as Jenner picked up Johansen's rebound and lifted it past Carey Price at 7:41. Johansen elected to shoot on a 2-on-1 and scored his first of the season at 17:11.
Jenner tied it on the power play 3:42 into the third when he scooped up Mark Letestu's rebound off Price's shoulder and put a backhand shot under the crossbar.
It looked to be headed for overtime when Plekanec surprised Bobrovsky and most of the crowd with his game-winning shot.
"He made it look like he was going to dish it off to the guy going with speed on the other side and then he just threw it across his body," Price said of the Plekanec goal. "I know it caught (Bobrovsky) by surprise because he was a good couple of feet off where he should have been."
The Canadiens started a five-game homestand that see them face Nashville on Saturday night. The Jackets end a three-game road trip Saturday in Washington.
Notes: Sean Collins, who made his first start of the season, replaced Gaborik. . . Had Bourque not played, defenceman Nathan Beaulieu would have skated on the fourth line. Beaulieu was scratched. . . Therrien announced that Max Pacioretty, who was injured Tuesday in Winnipeg, will miss three weeks with a strained left hamstring. . . Linesman Derek Amell of Port Colbourne, Ont, worked his 1,000th NHL game.