A frenetic affair played at a pace more akin to a cup final left nobody in any doubt about its importance.
At full-time the sight of the jubilant St Mirren players heading over to their supporters, while their Hearts counterparts trudged off, heads down and disconsolate, told its own story. This was a result that mattered.
St Mirren manager Danny Lennon had urged his players to adopt the mentality of a gladiator in front of a hostile audience and they did not let him down, throwing bodies in front of balls and lunging into tackles as if their lives depended on it.
The forwards did their part too, Steven Thompson popping up just as often in his own penalty box as he did in Hearts'. This was a collective effort and St Mirren reaped the benefits.
This was their first win of the season but there were other milestones too. St Mirren scored their first and then second away goals of the campaign and also recorded their first clean sheet. The result means St Mirren's last wins on home, neutral and away soil have all come against the same opposition. Most significantly, the victory carries them 12 points clear of Hearts and above Kilmarnock into 10th place.
After a difficult start to the season, there was much relief among the visiting ranks. It was a potentially significant outcome for Lennon as well.
Defeat would have shrunk his side's advantage over Hearts to just six points and might have prompted the St Mirren board of directors to consider a change in the dug-out. The win should offer Lennon some respite heading into the international fortnight although he was unusually subdued as he offered his assessment of a telling afternoon.
"I am glad at times like this that it's character that is required because I certainly know I have it in abundance in that dressing room," he said.
"I know I'm a fighter and those guys in there are fighters. There is no elevator to success, there's only the stairway. We took another couple of steps on that today."
John McGinn and Paul McGowan had both scored in St Mirren's previous victory - away to Kilmarnock on the final day of last season - so it was fitting both notched again here.
McGinn's brother Stephen had been the last player to score a winning goal for St Mirren at Tynecastle almost six years earlier and now here was his younger sibling getting in on the act. McGinn's goal after 42 minutes was the culmination of sustained St Mirren pressure that had yielded a raft of chances but nothing to really test Jamie MacDonald in the Hearts goal. Then came the breakthrough. Conor Newton fizzed in a cross that was missed by Kenny McLean in the middle but bounced to McGinn who headed beyond the goalkeeper.
If MacDonald was helpless at that one, he was culpable when St Mirren extended their advantage after 58 minutes. David van Zanten's cross should have been gathered by MacDonald but he grappled with it as if it was a wet bar of soap, presenting a simple chance for McGowan.
Yet a minute earlier Hearts had passed up a chance when Callum Paterson flashed a shot over the crossbar after sterling work by Ryan Stevenson.
It was another harsh lesson for Hearts' young players as they try to claw back the 15-point deficit foisted upon them as a result of the club's financial mismanagement. If there was one bit of good news for them it came in the form of Kilmarnock's defeat at Tannadice; the Rugby Park club are now in Hearts' immediate sights.
"There were defining moments in the game," admitted Hearts manager Gary Locke. "Callum [Paterson] had a wee chance at 1-0 and they went right up the park and scored. The boys are very down but, with having such a young team, we said at the start of the season it was going to be a big ask and after today it's not going to be any different."
Hearts rallied late on but couldn't find a way past Chris Dilo. Kevin McHattie belted in a free-kick that deflected off the wall and out for a corner, while a Jason Holt dart along the goal-line concluded with Dilo repelling him at his near post.
Hearts had nothing left to give. This was to be St Mirren's day.