They were totally outplayed and outclassed by Inverness, who by their own admission would admit to being one of the lesser sides in the league.
The visitors had all the answers, but the early lead given to them settled them down and allowed them to play all the football as they dragged Gretna from side-to-side, carving out openings seemingly at will.
Inverness got off to a flyer when they won a penalty in the second minute, correctly given by Michael McCurry who was well placed to spot a blatant push by David Cowan on Ross Tokely.
Thistle goal machine Dennis Wyness calmly sent debutant keeper Tony Caig the wrong way.
They doubled their lead on 31 minutes with a cracking free-kick. Don Cowie was the architect, sending a perfect 25-yard free-kick past the despairing Caig after a foul awarded against Danny Grainger when he brought down Wyness.
This came just after a huge let-off for the home side when Marius Niculae thought he had scored after a dreadful Gavin Skelton back-header had left the keeper stranded.
Just before half-time, Inverness almost went further in front but Roy McBain's shot fizzed across the face of the goal and just wide.
Gretna made a change at half-time, but it was Inverness who kept on the offensive as Wyness and Ian Black both came close in the opening minutes of the second half.
Gretna's Fabian Yantorno was sent clear of the defence, but his lofted effort was just off target and rolled wide.
Midway through the second half Gretna almost grabbed a lifeline when Skelton rifled in a brilliant shot that produced an equally good save from Michael Fraser, who managed to get the ball out for a corner.
On 73 minutes, Inverness grabbed the third when Barry Wilson produced a fine piece of play before working a one-two with Wyness and then calmly slotting past the helpless Caig.
Two minutes later the game was well and truly over when McBain left the best until last by unleashing a superb 25-yard screamer that hit the underside of the bar on the way in.