The Montreal Impact are in by the skin of their teeth.

Holding a 2-0 aggregate lead over Costa Rica’s Alajuelense heading into Tuesday night’s Scotiabank CONCACAF Champions League semifinal second leg, the Impact conceded four goals but managed two of their own to secure a 4-4 aggregate draw and the critical away goals tiebreaker to send them through to the tournament final.

Jack McInerney scored what looked to be a series-changing goal just before halftime, but Alajuelense fought back with two of their own before Andres Romero finished off a well-worked move in the 72nd minute, leaving the home side needing three goals to advance. They got two of them, leading to a nervy ending reminiscent of the Impact’s collapse in 2009, but after an emotional 90-plus minutes, Frank Klopas’ outfit became the first from Canada to reach the title round of North America’s premier club competition.

Alajuelense, backed by a vociferous crowd, came out flying in the first half, but the Impact were happy to take the air out of the game with a two-goal aggregate advantage stemming from their first-leg win in Montreal two weeks ago.

The game took a seemingly decisive turn in the 42nd minute, when Ignacio Piatti found Dominic Oduro after some nifty work. The Ghanaian – deployed as a right winger – hit a precise cross into McInerney, who buried it at the near post to stun the boisterous home support.

But Alajuelense would turn the game on its head just two minutes into the second half. After they wasted a number of promising free kick attempts in the first stanza, midfielder Pablo Gabas finally got it right, curling one into the top corner to put some life back into the encounter.

The home crowd was then dreaming of an epic comeback in the 60th minute, when Gabas got his second of the game. He found himself free after a flicked-on corner kick, and got a dash of luck as his side-footed finish clanged off the underside of the crossbar and bounced just across the goal line.

With Alajuelense needing to fight back throughout the game, there was certainly no shortage of emotion, with both sides getting involved in extracurriculars. Both McInerney and Gabas received yellow cards for a coming together as the former was substituted in the 70th minute. Both sides saw off-the-ball incidents throughout the game go unpunished by Salvadoran referee Joel Aguilar.

Two minutes after dodging a potential bullet when McInerney only saw yellow for his contact with Gabas, Montreal would deliver a killer blow through substitute Romero after both Oduro and Patrice Bernier passed on shot attempts to set up the Argentine, who got the Costa Rican 'keeper to collide with his own defender before calmly finishing past the defender stationed in the goalmouth.

The Costa Rican comeback gained new life, however, when Armando Alonso slipped a low cross past the Impact back line to Allen Guevara, who slammed home the finish in the 79th minute despite hints of an offside.

And Impact fans – whose team conceded twice in stoppage time to suffer elimination in a 2009 quarterfinal against Santos Laguna – surely had images of that collapse playing through their heads after Jonathan McDonald managed to tuck one home in the third of four minutes of stoppage time, but it wasn’t quite enough to quiet Montreal’s historic run.

Montreal will find out their final opponents on Wednesday, as another Costa Rican outfit, Herediano, travel to the Estadio Azteca to face Club America holding a 3-0 aggregate lead. The winner of that series will host the first leg of the CCL final on April 22, with Montreal hosting the return leg on April 29.