He produced a fantastic finish to prevent the game finished goalless as Gretna closed their campaign with a victory.
Hearts spent 65 minutes short-handed after teenage striker Gary Glen was sent off and had the better chances to win it late on.
If this was to be Gretna's last game it was not one to remember as the Fir Park pitch was not conducive to free-flowing football.
Gretna looked the hungrier for the points as they dominated the early stages as Hearts struggled to get going. Nicky Derverdics should have put Gretna ahead when he had time and space in the penalty area, but he fired his shot wide.
Hearts' task was made all the more difficult when Glen was sent off after 25 minutes when he kicked out at Craig Barr, leaving referee John Underhill with no option but to send him off.
Steven Hogg had a chance shortly afterwards when Hearts were caught short at the back but he hurried his effort and failed to trouble Steve Banks.
Skelton was fortunate to escape a red card after he kicked out at Laryea Kingston but Mr Underhill decided only to brandish a yellow card.
Banks was called into action to save a head-flick from Danny Hall from a Deverdics' free-kick, before Hearts came back and Greg Fleming saved well from Fernando Screpis, with Jamie Mole looking for any scraps in the penalty area.
Kingston came close for Hearts shortly before half-time when he curled a shot just a foot wide when he was given too much space by the Gretna defence.
Rostyn Griffiths thought he had put Gretna ahead moments later when he turned the ball into the net after Banks had saved from Deverdics, but the effort was chalked off for offside.
Mole had a good opportunity early in the second half after Screpis had put him through but he lofted his shot over the crossbar.
Gretna replaced goalkeeper Fleming with back-up Artur Krysiak, on loan from Birmingham, given the chance to show what he can do.
He was tested early by Mole and did well to get down to beat the ball out for a throw-in.
Kingston looked like the one player capable of sparking things for Hearts and he fired a shot straight at Krysiak with 20 minutes left.
It took Hearts 74 minutes to win their first corner and even then Kingston's flag-kick was pretty woeful and Gretna were not threatened.
Hearts looked set to score when Kingston raced clear to lay the ball off to substitute Kestutis Ivaskevicius, but his four-yard shot was brilliantly blocked by Krysiak.
It was then Gretna who stole the win when Skelton struck right at the death.