Jamie Mackie boosted Plymouth's survival hopes with the goal which sank Derby in a 1-0 win at Home Park.
The striker, a reported target for the Rams this month, showed their boss Nigel Clough just what he is capable of with his fifth goal of the season eight minutes from time.
But Derby, who took until December to win their first away game of the season but arrived in the west country unbeaten in five on the road, should have been home and hosed by then.
Rob Hulse passed up a host of opportunities for the visitors and Paul Green rattled a post in the second half.
Derby had the better of the early stages with Robbie Savage playing in Green, who shot over, and DJ Campbell heading Lee Johnson's free-kick wide.
Hulse then fired his first shooting opportunity over the top and a Green cross was almost turned into his own net by Argyle defender Kari Arnason.
But Plymouth had their moments and Carl Fletcher should have done better with a shot which he put wide.
It was overlapping Argyle full-back Karl Duguid who had the first shot on target but it flew straight at Rams keeper Stephen Bywater.
And just before the break Rory Fallon met a dangerous cross from Chris Clark but planted his header a yard over Bywater's crossbar.
In the second half a slick move from Derby saw Johnson play in Stephen Pearson and his cross found Hulse, who blazed over again.
Argyle went back on the attack and Mackie's shot flew over before Arnison put a header wide.
Hulse squandered another chance when he was teed up by Jay McEveley but drilled his shot the wrong side of the post.
And when the striker saw another effort deflected away from goal the ball fell to Green, who thumped his angled shot against the post.
Hulse knew it was not going to be his night when he turned on a sixpence and drilled in a low shot only to see the wrong-footed Argyle keeper David Stockdale - making his debut on loan from Fulham - save with his legs.
And as the clock ticked down Derby failed to clear a free-kick from Luke Summerfield and Mackie was on hand to lash home the loose ball.
The victory saw Paul Mariner's side leapfrog Reading into 22nd and leaves them just three points from safety.
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