Kris Boyd took his tally to six goals for the season as the Kilmarnock striker's double again leaves Hearts once again facing a 15-point gap to survival.
Gary Locke's men went down 2-0 at Rugby Park after the former Scotland frontman struck once in each half.
The Jambos - deducted 15 points for entering administration in the summer - had clawed back the deficit on their rivals St Mirren to just nine at the beginning of this month but the defeat to Killie now means they must start all over again.
The victory is Killie's second in succession thanks mainly to Boyd's instinctive finishing capabilities.
But the Scottish Premiership's record goalscorer showed he has improved the other facets of his game too as he worked impressively to link up with his team-mates.
It was a bruising encounter that left both teams tending to casualties as Ryan Stevenson limped off with a knee injury for Hearts before Kilmarnock defender Darren Barr left the filed on a stretcher with a worrying head injury.
But what will really concern Locke is the meek body language of his troops. Having started the season with seven points out of the first 12 available, Hearts have allowed their early momentum to fade away.
They arrived at Rugby Park to face a side buoyed by their first win of the season against Ross County last week having themselves added just one further point to their tally in their previous six games and sitting still in negative equity.
Yet the home side's form was of such a fragile nature that even the confidence gained by beating the Staggies lay on a knife-edge and their chances were hardly helped by the loss of playmaker Rabiu Ibrahim following his collapse against Derek Adams' men.
Hearts knew the consequences of defeat would be dire, even at the early stage in the season, and started with purpose as Stevenson forced Killie keeper Craig Samson to tip over his own bar with a dipping shot six minutes in.
But Kilmarnock were equally as desperate to get turn the screw on the visitors as Boyd came close with a rasping strike following Danny Wilson's loose header for the visitors.
And the Scotland defender was culpable once more as Boyd stuck the opener. Collecting Sean Clohessy's pass on the edge of the box, the former Rangers man still had work to do if he was to threaten but Wilson's slip opened up a path to goal as Boyd then calmly took his time, dummied Jordan McGhee and then fired past Jamie MacDonald in the Hearst goal.
There was a further blow for Locke's side when Stevenson - who had already missed two months of the campaign with a knee injury - limped off again on 20 minutes to be replaced by Callum Paterson. The substitutes' first involvement, though, was to clatter heads with Barr, with the home defender coming off the worst as he was then carried off wearing a neck brace.
The former Jambos man was replaced by Sammy Clingan but the replacement did not slow down Killie, who should have added to their lead when first Barry Nicholson misses an easy header at the back post before Boyd then shot over from 15 yards.
MacDonald was then forced to beat away Johnston's effort as Michael Gardyne benefited from Kevin McHattie's slip before playing in his team-mate.
Hearts' problems stemmed mostly from an inability to retain possession and they persisted after the break. It was precisely that flaw in their make-up which let in Clohessy to fire at MacDonald on 59 minutes but the keeper again came up with the save.
But there was little he could do as Boyd came up with his second of the afternoon. Brad McKay was caught ball watching underneath Clingan's long free-kick and Boyd took one touch before clipping it over MacDonald from a tight angle.
The keeper did save from Johnstone on 72 minutes as again the visitors gifted possession cheaply, while McKay made up for his earlier mistake by bravely blocking from Boyd just five yards out.