Paul Cook was hoping to see his team get back to winning ways after consecutive away defeats - but he was in for a shock with his side capitulating in four first half minutes.
It didn’t get much better in the second half, with Swindon monopolising much of the play.
Swindon certainly had their fair share of the early exchanges.
Louis Thompson had a couple of chances, yet Chesterfield tried to assert themselves with Jimmy Ryan and Dan Gardner both having a pop at goal.
Just before the half hour, former Sheffield United man Yaser Kasim despatched a possibly deflected free kick to the top left corner to give Swindon the lead.
It was harsh on Cook’s team, they’d had something of a purple patch beforehand.
But they fell apart four minutes later; Nathan Byrne converting from outside the box to the top right corner.
Under rainy skies, what had looked like a promising night was certainly turning bleak.
Sam Clucas headed over and Sam Morsy was shown a yellow card (one of three for the home side on the night) as the bad news continued.
When the second half started, Swindon continued to look threatening, Byrne in particular, a sliding tackle needed to snuff out the danger.
On 52 minutes, Cook rung the changes.
Daniel Johnson replaced Dan Gardner and Gboly Ariyibi came on for Jimmy Ryan.
It didn’t stop the flow.
Michael Smith had two chances to further punish the Derbyshire outfit.
And it could have been three when Town hit the woodwork with a header from Jonathan Obika.
It was game over with 20 minutes left, though.
Andy Williams rounded Tommy Lee and placed it coolly over the line for 0-3.
Michael Smith then came within inches from making it four.
With the clock ticking away there was a sequence which summed up the night: Eoin Doyle, Ariyibi and Daniel Johnson all unable to bury chances.
Chesterfield: Lee; Darikwa, Evatt, Margreitter, Jones; Gobern, Ryan; Gardner, Morsy, Clucas; Doyle.
Subs: Hunt, Raglan, Banks, Johnson, Ariyibi, O’Shea, Humphreys.
Swindon: Foderingham, N.Thompson, Byrne, Luongo, Stephens, Turnbull, Kasim, Smith, Bell, L.Thompson, Obika.
Subs: Gladwin, Williams, Reeves, Toffolo, Barthram. Belford, Rodgers.
Ref: Duncan Scott (Newcastle)