Goals from Curtis Main and Alex Gogic helped St Mirren take a huge step towards a top-six finish - and heaped pressure on Robbie Neilson.
You had to go as far back as 2013 for St Mirren's last win at Tynecastle but Stephen Robinson's men were well worth the three points as furious scenes erupted in Edinburgh.
It had already been a testing week for Neilson after graffiti was daubed outside the stadium calling for his exit.
Come 5 o'clock on Saturday, it was even worse with a significant section of Hearts supporters raging over Neilson's tenure.
Main sparked contrasting emotions between the supporting factions inside Tynecastle after 52 minutes. The powerful striker outmuscled Kye Rowles before lashing home a fizzing effort into the bottom corner.
Five minutes later and Alex Gogic inadvertently turned home to condemn Hearts to a fifth consecutive defeat.
A long throw into the Hearts box fell to Mark O'Hara who blasted into the ground where the ball flicked up off Gogic to wrongfoot Ross Stewart.
A miserable afternoon for Hearts was rounded off just after the hour when Robert Snodgrass was given his marching orders for a second yellow card.
PRESSURE MOUNTS ON ROBBIE NEILSON
It was an intriguing atmosphere in Tynecastle before kick-off with an expectant crowd demanding a reaction to a four-game losing streak.
Neilson himself said midweek that Hearts had to respond with victory - but the outcome at Tynecastle was quite the opposite.
What started with a few stray shouts calling for Neilson to consider his position ended with desperate scenes at full-time.
Ferocious boos erupted after St Mirren opened the scoring, and before long it was full-on chants of "Neilson, get to f***" as the visitors doubled their advantage.
Impassioned supporters then were quick to voice their opinion on the Hearts manager's position as he walked down the tunnel.
If the response during the match was tough, the barrage of abuse faced heading off the pitch must've been torture for the under-pressure Hearts manager.
SAINTS MARCH FOR TOP SIX CONTINUES
This time last season, St Mirren were looking over their shoulders at the drop. This result shows how much difference a year can make.
Stephen Robinson has his charges well drilled, difficult to beat and crucially packed with ability.
The win takes St Mirren into fifth and just three points off Aberdeen in third and five points ahead of Livingston in seventh.
At this stage, all things look set for the Paisley side to claim an elusive top-six spot.
At full-time St Mirren fans serenaded their stars with chants suggesting a Europa League spot is on the cards.
For Robinson, it's not over until a top-half spot is mathematically sealed but there is little to suggest the Buddies won't start aiming even higher than just a spot in the top six.
Continue on current form and it might just become a march for European football.
SHANKLAND SOLO MISSION
So often heralded as an impressive footballing side, Hearts lacked any of the vibrancy, energy and drive associated with the club.
Neilson's men looked lost at times and devoid of confidence as they slumped to another defeat.
Captain Lawrence Shankland - standing in for Craig Gordon - was one of few to receive pass marks as he tried to take control of the game but was just too isolated both in his position and his endeavours.
The Scotland striker was far too often forced to drop deep and even wrangle the ball back within his own half rather than show his penalty box prowess.
