The Flames took over for a good chunk of the period, but the homeside found life late in the stanza, forcing Smith to be at his very best to keep his team ahead.
First, a massive pad save off a Landeskog blast. Then, a big-time blocker stop off MacKinnon, followed closely by a Carl Soderberg one-time blast, and a breakaway try by Rantanen.
In all, the Avalanche piled 12 shots in the final 5:35 of the period, but Smith - forever the showman - was putting on the concert of a lifetime.
The Flames opened up a 2-0 lead at 6:58 of the third when Ryan plunged home a loose puck at the side of the net, but the Avs finally solved Smith and made it a one-goal game again less than three minutes later.
J.T. Compher was the beneficiary of a rebound in the high slot, slinging a shot top-shelf just 1:12 after the Ryan marker.
"In the third, we were good up until their goal," Giordano said. "They got some real momentum, obviously, and they scored a late one to tie it.
"We just have to regroup here, get back home and know that we lost two in overtime. The only one that has really been out of hand was the last one. Tonight we just couldn't stop the momentum after they got their first one and we've got to do a better job than that."
The Flames got back to their game early and did a significantly better job in transition, using their speed and preventing the counter-attack with extended periods of zone time.
Coming off a disappointing Game 3 loss - they couldn't have asked for much better.
Shots did favour the Avalanche 15-13 after one, but neither side had much of an edge.
However, Calgary's immaculate puck-stopper was once again in fine form, picking up right where he left off after scoring post-season career-high 50 saves on Monday.
There was a menacing moment late in the first, though, when Colin Wilson drove the net on a partial 2-on-1, lost his edge at the lip of the blue paint crashed heavily into Smith, causing all sorts of concern on the Flames bench. Athletic therapist Kent Kobelka swiftly tended to the fallen netminder, worried Smith - who was favouring his right leg after the skate-first impact - may have been cut. Thankfully, that wasn't the case and the veteran stayed in the game, no worse for wear.
He's a fighter.
Has been all series.
And they'll need him again on Friday as the Flames begin a stretch of three must-win games.