They'd squandered a 3-games-to-1 lead. Allowed the Rottweiler to bite through the leash.
"Nobody,'' reasons Al MacNeil, the Flames' coach at the time, over 36 years after the fact, "had given us a chance, so much as a second-thought, when the series began.
"So what made Game 7 any different."
The relocated Flames, in their first season out of Atlanta, in preposterous search of a spot in the Stanley Cup semifinals.
A three-game sweep of the Chicago Blackhawks, the franchise's first-ever playoff series success, netted them a quarter-final date with the bully-boy Philadelphia Flyers.
Only the year before, the two-time Stanley Cup champs had gone a record 35 consecutive games without losing.
To no one's surprise, Philly cruised in Game 1, 4-0.
Much to the shock of Bobby Clarke, Bill Barber, Reggie Leach, et al, and to the amazement of the hockey world, the Flames then strung off 5-4, 2-1 and 5-4 wins.
The Flyers, nothing if not scrappy, fended off elimination via 9-4 and 3-2 scorelines.
So back to the belly of the beast, the most feared address in all of hockey, 3601 South Broad Street, site of the now-demolished Spectrum.
"Going into the Spectrum back then,'' recalls Jim Peplinski, "was like that moment in Gladiator, remember, where the guys are walking into the Colosseum and few of them are peeing their pants.
"You get the picture."
Defenceman Bob Murdoch echoes the feeling of menace opposing teams were subjected to.
"To get to the ice, you had to go past all this wall of people saying whatever they damn well pleased. And they weren't exactly tossing compliments your way.
"It was total intimidation.
"The thing about playoffs, though, is that stuff like that, it just feeds into the energy and emotion of BOTH teams.
"Looking back, despite that being such a difficult building to go into, we felt really comfortable playing that game."
What might've been forgotten in the build-up was that the Flames had a sizeable lineup themselves, more than enough toughness to stand up to any skullduggery.
And Philly's over-zealousness would, in the final analysis, be its undoing.
A too-many-men bench minor at 1:26 allowed Flames' winger Willi Plett to cash a deflection past goalie Rick St. Croix for a 1-0 lead. A tripping minor to Paul Holmgren then led to a Ken Houston poach at 8:21.
When all was said and done, Calgary's powerplay had gone 3-for-8, Philadelphia's 0-3.
"Bruce Hood refereed that night,'' Peplinski remembers. "He called, if memory serves me correctly, three elbowing penalties' - holding, tripping and elbowing, actually (on Paul Holmgren).
"I couldn't believe that a referee would go into the Spectrum in Philadelphia at that time, in 1981, and call three penalties like that in such an important game.
"To have that kind of courage … I said to myself 'Bruce Hood, you have a pass from me for the rest of my life.'"
Against all odds, the underdog Flames ran out 4-1 winners that night.
"The only problem,'' reflects MacNeil, "is that we'd put so much into beating Philly, it was almost like our season, our Stanley Cup.
"The attitude of the guys seemed to be: We'd expended everything we had right there, wagered all the chips in our pile, in that series.
"We never could find the same sort of emotion or energy against Minnesota."
Calgary would fall in six to the Stars at the second-last hurdle.
For the full listing of our 37 for 37 moments and links to past stories, check out: