As mentioned, it was another tough outing against Vegas, who had beaten Calgary 6-2 on Oct. 12 and 6-0 on Nov. 17.
This score was much closer - but that was, of course, little consolation to a Flames team that fell behind 3-0 but battled back to tie it up with three minutes to go in the third period.
Matthew Tkachuk had knotted the contest up, bringing the crowd to its feet with a prolonged deafening roar, but Shea Theodre's tally 1:10 later broke the hearts of the C of Red. Vegas added an empty-netter to seal it.
The Flames are now 3-8 all-time in regular-season matchups against the NHL's most recent expansion cousin.
The loss also marked their first defeat on this five-game homestand after opening with a pair of wins over Columbus and Arizona.
David Rittich got the start after watching Cam Talbot man the cage the previous three tilts, and he made a huge stop early, less than a minute into the contest.
Nicolas Roy held the puck on a two-on-one, trying to freeze Rittich, who came out to challenge, and then attemped to put the puck around and behind him.
Big Save Dave kicked out his right pad to make the stop, then covered the puck a few feet outside his crease, leaving Roy to look up and shake his head as he skated away after the whistle.
The Golden Knights did open the scoring after a great play by Ryan Reaves, the big winger sweeping the puck over the blue-line in one motion and skating in hard to get a shot on Rittich, the rebound sailing out into the slot amid a maze of bodies, the trailing Tomas Nosek firing it home into a wide-open cage at 5:24.
Vegas then capitilized on a two-on-one at 11:49, this time Nick Cousins passing across to another Nick - Holden - who snapped it home before Rittich could come across the blue paint.
The red-hot Mikael Backlund - who had 21 points in his last 15 games; six in his last five - appeared to open the scoring with 4:10 left in the period, tipping a point-shot from TJ Brodie, and then getting a second whack at it and pushing it home past Robin Lehner.
Called a goal on the ice, Vegas challenged for goaltender interference and after review, the officials overturned it.
With captain Mark Giordano in the box for tripping in the second, Backlund skated the puck up the ice short-handed and drove around a Vegas defender, fending him off with one arm, for an in-tight chance that Lehner stopped, hugging his goal-post.
On the ensuing Vegas drive down the ice, Max Pacioretty scored to make it 3-0.
Later, Matthew Tkachuk took a feed from Backlund and fired a shot beat Lehner but clanged off the post.
The Flames finally got on the board at the 8:23 mark, when Milan Lucic picked up a puck inside Calgary's zone and started a three-on-one rush, keeping it and sliding a wrister along the ice five-hole for an unassisted tally.
