The Flames scored three unanswered goals in the first 2:49 of the third period to dump the Leafs 4-2 at the Scotiabank Saddledome Thursday night.
It was the seventh straight win for the Flames, who remain undefeated under interim coach Geoff Ward.
Johnny Gaudreau scored two of those three markers in the final frame as the Flames continue to climb in the Western Conference standings.
David Rittich made 32 saves and played an equally big part in the win.
John Tavares opened the scoring for the visitors at the 8:24 mark of the first period with his 13th of the season.
Mitch Marner made an incredible trailing pass as he circled behind the net, the puck snapped back on such a tight angle it barely missed hitting the post but squeaked by and sailed out into the slot where it found its target - a streaking Tavares, who snapped it home.
The Toronto captain scored twice and added a helper in the Leafs 4-1 victory over the Canucks Tuesday in Vancouver. Prior to that, he'd been held without a goal in three outings.
Later in the frame, the Flames had two Grade-A chances to tie it up.
First, Dillon Dube beat an icing call and passed the puck out to TJ Brodie, who missed wide on a backhand.
Later on a rush, Tkachuk had the puck knocked off his stick just as he was about to shoot, the biscuit going right to Elias Lindholm who tapped it to Andrew Mangiapane at the side of the net but his tip was stopped by Andersen who just made it across to the post.
Third time was the charm, though, as Travis Hamonic scored his second of the campaign at 16:23.
Sean Monahan brought the puck into the zone and curled back to the blueline before spinning and taking a few strides towards the net to buy some time. With all Toronto eyes on his side of the ice, Hamonic skated in as a trailer on the far side and took a feed and snapped it home high short-side through a small window above Frederik Andersen's glove.
The added bonus of the tally, as with all Hamonic's markers, was the crowd getting to hear a little MC Hammer - his goal celebration song.
The Flames had a few chances on the powerplay to end the opening period and through the first 15 seconds of the middle stanza, but nothing doin' in the two minutes of extra-man time.
Not long after, it was time for some ooooohhhhs and ahhhhhhhs at both ends of the ice, first Monahan bringing the puck into the zone and instead of shooting, trying to send the puck cross-crease for what would have been a tap-in for Gaudreau, but the puck going off the skate of Kasperi Kapanen.
Then at the other end, it was Marner taking a nice pass as he slipped into the slot but Rittich making a glove stop.
Andersen soon after flashed the leather himself to catch an offering from Gaudreau as the Flames forward sailed in down the left side and let one fly from the face-off circle before he was headed off by a Leafs defenceman.
Mixing it up a bit, Rittich then had to drop in the splits and kick out his left pad to stop a shot from Zach Hyman who was parked right on the doorstep.
Marner made it 2-1 at 14:06 when he took a pass from Tavares and wired one right under the crossbar and in.
That gave the Leafs an extra kick in their step, and they poured on the pressure with a handful of shots in the following three minutes.
The Flames had a push of their own before the final whistle of the frame, the shots 22-17 for the Leafs after 40 minutes.
Then came the onslaught.
Just 19 seconds into the third, Gaudreau scored his eighth to tie it up.
Andersen tried to clear the puck around the boards from behind his net, Mikael Backlund heading it off and passing out to Gaudreau, who fired it in the same spot as Hamonic.
With Lindholm already in the box for a trip with just under five minutes gone, Hamonic was sent off for delay of game after putting the puck over the glass.
That gave the Leafs 1:35 two-man advantage.
Auston Matthews did ring one off the post with just 20 seconds left in Hamonic's penalty but the Flames penalty-kill - which came into the night 8th in the league at an impressive 83.6% efficiency - managed to hold the fort.
The Leafs pulled their goalie with more than three miutes to play to no avail.
THEY SAID IT:
Gaudreau on the rally:
"We knew we needed a strong push to start the third there. We got three quick ones and played well with the lead."
On his play:
"I'm getting good looks, obviously playing with a lot of different players. You get different looks playing with different players. It's been great. I've been getting a lot of chances and found a way to put a couple in tonight."
Johnny on Ward:
"He expects a lot out of us, but we like playing for him and he runs a great practice, I guess, and does a great job on video and stuff. For him to go 7-0 with never being an (NHL) head coach before is pretty impressive. We enjoy playing in front of him."
Frolik on wild win:
"It was fun for the fans. Overall, it was a good game. Even being down 2-1, we said in the room, 'it's just one goal.' Just go out there and leave everything on the ice in the third. We turned it around and it was a great win."
Rittich joking about Gaudreau:
"I don't know. He still can't score on me. I don't know if he's 'back.' I'm happy for him and hopefully he has more on his stick."
On team in front of him:
"You could see guys back-checking all night long and were fighting for blocked shots and stuff like that. It's little things, but they make a big difference."
Ward on the comeback:
"It's been a bit of a theme lately, but our team's been pretty resilient for probably the last three hockey games. Tonight was no different. I think the added bonus for us tonight was, behind down going into the third period, they put a push on right at the beginning of the third and we were able to get them back on their heels and score a couple goals. I thought our group stayed composed, I thought they stayed on task, and I thought they played to the process. We didn't change what we were trying to do. We just kept playig, we just kept playing, and eventually we got rewarded for it."
This is the first of two matchups this season between the Flames and Leafs. They meet again Jan. 16 at the ACC. They split the season series in 2018-19 with both teams winning on the road ... The Flames have a record of 10-3-1 against Eastern Conference opponents and a record of 6-0-0 against the Atlantic Division ... With his goal on Tuesday (the 389th point of his career), Monahan passed Joe Mullen for the 15th most points in Flames franchise history.