But the visitors managed to snatch their first ever point in the Scottish top-flight with Craig Barr cancelling out a superb opener from Hearts' Andrew Driver.
Laryea Kingston was surprisingly left on the bench by the Jambos, with the usual glut of Lithuanians filling the Tynecastle side.
Gretna were able to give a debut of fire to new signing Aurelien Collin, who slotted straight into the heart of the rearguard.
It was the home side who almost took the lead after only 30 seconds as Lee Wallace's cross was almost diverted into his own net by Paul Murray.
Hearts dominated the majority of the first-half possession but some resolute defending from the SPL newcomers consistently thwarted the Edinburgh club.
Poor finishing from the Jambos did not help their cause as Andrius Velicka had a gilt-edged chance to gift the Tynecastle club the lead but the Lithuanian scuffed his shot from point-blank range.
Tactical tinkering at half-time was the order of the day as Kingston and Driver took the field for the Jambos, while David Graham suited up for the visitors.
Kingston was so keen to start his season that the midfielder ran straight onto the pitch, forgetting to conclude the official formalities much to the amusement of his coach Stephen Frail.
Driver did not take long to get into the action, latching onto a Velicka flick but Fleming, who was having a superb shift in the Gretna goal, raced from his line to parry at the youngster's feet.
It was the talented winger who broke the deadlock with one of the best goals that has been witnessed at Tynecastle for a long time.
Some industrious play by Andrius Ksanavicius on the left flank found Driver unmarked on the edge of the area and the winger's delicious left-footed volley looped over Fleming and into the back of the net.
Gretna thought they had equalised almost immediately after the restart as Kenny Deuchar's 16-yard effort beat the despairing dive of Steve Banks, only for Juho Makela to clear off the line.
But the visitors stunned the Tynecastle faithful by sneaking an equaliser with fifteen minutes left to play.
An innocuous free-kick from Fabian Yantorno reached the back post where Barr was on hand to prod the ball over the line.