The Calgary Flames added another implausible chapter to the fairy-tale story of the 1981 Stanley Cup playoffs tonight. In the unfriendly confines of the Spectrum, the Flames thumped the Philadelphia Flyers, 4-1, in the decisive seventh game of their quarterfinal series.

That sent the Flames, seventh in the regular season, home to open the semifinals against Minnesota, No. 9, while the New York Rangers, No. 13, challenge the lone survivor among the top six, the first-place New York Islanders.

Calgary jumped ahead on powerplay goals by Willi Plett and Ken Houston in the first nine minutes, leaving the Flyers with the difficult task of catching up. They never did, partly because of goalie Pat Riggin's 31 saves, and with five minutes left the faithful already were pouring out the exits, denied the victory party that seemed so certain after the Flyers won here, 9-4, Wednesday and evened the series Friday in Calgary.

"We came in with the attitude that there was a seventh game and anybody could win it," said ex-Flyer Bill Clement, the former Washington Capital captain who did a superb job killing penalties for the Flames. "I think maybe they expected us to roll over and play dead, and that was reasonable, considering the last two games. But we were sane enough to keep our heads and play disciplined hockey."

Calgary was helped by the officiating, not because it was one-sided but because referee Bruce Hood called what was there to be called. In other games, the Flyer have been able to intimidate opponents without paying a price. Tonight they paid heavily.

"Those penalties disoriented us right at the beginning," said defenseman Behn Wilson, one of the few Flyers willing to discuss the sudden end to their season, after having come so close to a Stanley Cup last year. "We weren't able to play our game. We like to establish ourselves in their end and maintain pressure, but with the penalties you back off a bit."

The first big blow for the Flyers came after just 86 seconds, when a substitution on the fly resulted in a penalty for too many men on ice, an oncoming player touching the puck before the man he was replacing had made it off.

Plett, left alone in front of the Flyer net, deflected a 40-foot shot by Guy Chouinard for a 1-0 lead at 3:03. The goal came on Calgary's fifth shot -- Philadelphia had none yet -- and was scored by the player who was suckered into a double misconduct penalty here Wednesday and missed Friday's game in Calgary.

"Plett is just important to us as (Paul) Holmgren is to them," Chouinard said. "A physical series like this belongs to a guy like Plett."

"I got a chance to work off some frustrations on the ice tonight instead of sitting in the stands crushing pop cans," Plett said.

The frustrations were building on the other side, however, and Holmgren was charged with four minor penalties in the first 25 minutes. The fourth brought owner Ed Snider of the Flyers out of his box with fist waving and mouth moving, but it was the second, for tripping Kent Nilsson, that hurt most.

Chouinard took advantage of the manpower difference by racing down the left wing and firing a perfect pass into the slot, where Houston sped in to convert it at 8:33.

A penalty to Flyer defenseman Glen Cochrane, for hooking John Gould, led to the third Calgary score, by rookie Kevin Lavallee.

With seven minutes left in the second period, the Flyers' Bill Barber netted a 35-footer off a faceoff in the Calgary end. It was Barber's 11th goal of the playoffs and 100th career Stanley Cup point.

But the noise generated by the 17,077 could not wring miracles from weary players struggling through their 12th game in 19 nights; not with Riggin grabbing everything headed his way.

The final nail was pounded home with 13:51 remaining by Nilsson, who missed Wednesday's game and skated short shifts because of a damaged knee. Nilsson wheeled around Bobby Clarke just inside the Flyer blueline, then fired a shot under the stick of defenseman Frank Bathe. Bob MacMillan, alone in front of goalie Rick St. Croix, deflected it in to complete the scoring.

The Flyers were bidding to become only the third team in Stanley Cup history to rally from a 3-1 deficit to pull out a series