A late penalty by Steve Davies shattered Forest Green hearts after they had led Championship opponents Derby County three times at the New Lawn.
The managerless Rams had to battle back from 2-0 and 3-2 down, but Darren Jones’ foul on Kris Commons with five minutes left saw him red carded and heroic Rovers sunk.
Brilliant goals in the 14th and 19th minutes by Jonathan Smith and Alex Lawless had put the home side in dreamland, but Rob Hulse reduced the deficit in the 39th minute before Martin Albrechtsen made it all square in first-half stoppage time.
It was almost even more of a fairytale start for Rovers, as within eight seconds Adriano Rigoglioso pounced on an error in the Derby defence and forced a smothering save from recalled goalkeeper Roy Carroll.
Carroll’s opposite number Terry Burton had to be alert to keep out a cross-shot from Commons in the third minute, but otherwise the hosts were almost entirely on the front foot.
The opening goal was an absolute peach. Carroll rushed out of his goal to deal with a long punt forward, but found himself stranded as Smith smashed into the top corner from 25 yards.
Simon Clist’ delightful through-ball carved the visiting defence open to create Rovers’ second, though Lawless still had plenty to do to with a superb finish past Carroll from a tight angle.
Derby’s reply stemmed from a free-kick by Commons, from which Lewin Nyatanga’s header come back off the crossbar and Hulse stabbed home the rebound.
Another Commons set piece caught Rovers out seconds before the break, enabling Danish defender Albrechtsen to net at the back post.
Momentum remained with the Championship outfit as the second period got underway, and they should have gone ahead on the hour when Hulse fired straight at Burton when clean through and Commons sliced the follow-up wide via deflection.
The hosts looked to be tiring, but they were given a massive lift in the 72nd minute when Stonehouse’s speculative shot crept past Carroll at the near post.
Suddenly the dream was back on, but four minutes later Green latched onto a cross-field pass and slotted tidily past Burton from close range.
The Rams’ superior fitness was now telling, borne out when Commons was scythed down from behind by a labouring Darren Jones – rightly sent off by referee Paul Taylor.
Substitute Davies gave Burton no chance with the spot kick, smashed into the top right-hand corner.