Knight was on hand in the 81st minute to drive a diagonal cross from John Thorrington low past Nathan Abbey in the Spireites goal.
Abbey was deceived by the flight of Knight's equaliser which was just about deserved after the Terriers picked up their game in the second half.
Town had been outplayed in the first half and, close to interval, Martin Booty had volleyed a deserved opener for Chesterfield in the 41st minute after Town cleared from Steve Payne's long throw but failed to follow up the loose ball.
Both 'keepers were kept busy during the match, Martyn Margetson kept his hands warm with one-handed saves from Marcus Ebdon and former Town man Steve Payne.
Nathan Abbey had to be ever watchful for tricks and shots from Leon Knight who sidestepped his way through the home defence and blasted a tricky Thorrington cross at him in the first half.
Former Emley striker Glynn Hurst was a pest for Chesterfield all night, chasing down all lost causes and making Nathan Clarke and Kevin Gray very nervous of his pacy runs.
Town's new look side had been outplayed for most of the match but Lou Macari opted for attack when he made his substitutions, bringing on Clyde Wijnhard and sacrificing Kenny Irons as they sought the equaliser.
Chesterfield had done their homework and harrassed the Terriers all over the pitch for most of the night but they had not counted on the ever-dangerous Leon Knight who, despite some dramatics during the second half, kept Town in the chase for promotion with his crucial goal.
Read Doug Thomson's match report in the Examiner on Wednesday. Have your say in the messageboard below - selected comments will be considered for publication in the Examiner.
Chesterfield (4-4-2): Abbey, Breckin, Ebdon, Booty, Hurst, Williams (Burt 84), Payne, O'Hare, Howson, Allott, Innes
Subs not used: Willis, D'Auria, Richmond, Blatherwick
Scorer: Booty 41
Town (4-4-2): Margetson, Jenkins, Clarke, Evans (Wijnhard 77), Gray, Thorrington, Schofield, Holland, Irons (Moses 88), Facey, Knight
Subs not used: P. Senior, Heary, Hay
Booked: Knight, Irons
Scorer: Knight 81
Referee: Paul Rejer (Tipton)
See subsequent pages for match points
94 mins: Schofield chipped the ball into the box as the Terriers attacked one last time.
92 mins: Knight's headed was well wide.
90 mins: The game went into added time as both sides appeared to be settling for the point.
88 mins: Adrian Moses was ready to come on to replace the tiring Kenny Irons - Town seemed set to settle for a point as they re-shuffled.
86 mins: Clarke tackled Hurst and sent up a counter-attack.
86 mins: Steve Payne's left footed shot came off Irons' backside.
81 mins: Leon Knight struck again as his measured low shot from John Thorrington's diagonal ball defeated Abbey! Departing Town fans scuttled back to their positions as the game headed for an exciting end!
79 mins: Abbey made a sliding clearance to collect from behind Leon Knight.
77 mins: Lou Macari went for broke as he pulled Gareth Evans off and replaced him with Clyde Wijnhard. Town went into a 3-4-3 formation to seek the equaliser.
76 mins: Schofield's cross was too close to the 'keeper as Clyde Wijnhard prepared to come on.
74 mins: Mark Allott miskicked with the Town goal at his mercy!!
73 mins: Breckin's shot fell to Margetson.
73 mins: Gray headed a corner away.
71 mins: Breckin cleared twice but Town had already been adjudged offside.
70 mins: Breckin conceded a free kick 25 yards out - a great chance for Town.
68 mins: Williams nicked the ball from Schofield as he tried to find a path upfield.
67 mins: Holland tried one trick too many and slipped over the ball.
65 mins: Delroy Facey's ferocious turn and drive was parried away by Abbey after a great move involving Thorrington.
63 mins: Leon Knight was booked for diving as the game slowly turned to frustration for Town.
62 mins: Breckin headed wide from a Spireites corner.
61 mins: Irons gave the ball away and Hurst almost broke free before the referee blew for an infringement.
60 mins: Booty's high challenge felled Jenkins. The Welshman wasn't happy with the dangerous tackle and made his feeling known when Booty went over to offer his hand.
57 mins: Thorrington was caught from behind and won a free kick.
56 mins: Hurst beat Gray after chasing him down and tested Margetson again. Town were warming up their substitutes.
53 mins: Irons was penalised for a late tackle on Williams. He was booked.
52 mins: Hurst pulled away from the defenders and struck a sweet shot which drew a great save at his near post by Margetson.
51 mins: Schofield's rasping effort drew a save from Abbey.
49 mins: Facey was deemed offside after an incisive run by Kenny Irons saw him wait too long before releasing the ball to the attacking players who were already chasing upfield.
48 mins: Town put the pressure on but Irons' free kick was wasted.
46 mins: Town kicked off looking for the equaliser.
Martin Booty hit a volley from a poorly cleared long throw by Steve Payne to give Chesterfield a late lead they narrowly deserved.
Town were second all over the pitch and were being muscled out of a generally open game and had to rely on Martyn Margetson to produce two great one-handed saves to keep the Terriers in it.
Leon Knight produced Town's best chance - an effort which forced Nathan Abbey to palm the ball away.
45 mins: Ebdon's injury time free kick was wayward.
44 mins: Knight slipped on the ball after the Holland passed it to him.
43 mins: Williams retailiated against Holland after the ball had gone during a challenge. The referee didn't see it. Gareth Evans and Glynn Hurst squared up as well.
41 mins: Martin Booty hooked the ball over the static Town defence from a long throw by Steve Payne. Booty was not picked up!
38 mins: Innes wasted some good possession with an abortive attack.
37 mins: Schofield was offside after a well planned Town set piece after Thorrington put in a great pass.
35 mins: Knight tried to pull the ball across the 6 yard box but won a corner after much persistence.
34 mins: Knight beat one man but miscued his next touch.
33 mins: Breckin beat Knight to the ball and cleared.
32 mins: Booty's right footed shot was wide after Kevin Gray reacted too slowly.
30 mins: Knight was caught by Payne after he had rounded him and lined up a shot.
28 mins: Steve Payne forced another one-handed Margetson save after the ball broke for him with Town defenders far away and caught deep.
27 mins: Chesterfield won a free kick after Kevin Gray clattered one of their players. He got up gingerly and limped away.
26 mins: Thorrington attacked and won a corner.
25 mins: Knight turned, dragged the ball back and squeezed between two defenders in an amazing move before being chopped down by another defender.
24 mins: Abbey parried away Knight's blast after Thorrington delivered a sweet low cross to the penalty area where the young striker was lurking.
22 mins: Knight tussled with Williams after a heavy tackle.
21 mins: Irons' free kick struck the wall. Gareth Evans took control on the break but his cross was too near to Abbey.
21 mins: Thorrington was shoved as he tried to find the Town runners.
20 mins: Margetson clutched the ball in spite of pressure from Hurst.
18 mins: Ebdon and Payne combined to allow Ebdon a strike which was tipped away one handed by Margetson. The Spireites were hungry for the goal and were exploiting the space in front of defence.
15 mins: Payne won the ball off Knight but they couldn't use the ball.
12 mins: Abbey scrambled for the ball after Danny Schofield caused problems in the Spireites defence.
11 mins: Evans forced Clarke to backpedal to receive a back pass.
8 mins: Glynn Hurst struck a dipping shot which had Martyn coming across to cover before it bounced wide.
7 mins: Jenkins combined with Thorrington but the American was forced wide and O'Hare conceded a throw-in.
5 mins: Facey chased down a long clearance by Nathan Abbey was quick to collect.
3 mins: Margetson had a wide shot well covered.
2 mins: Glynn Hurst outpaced the ball-watching Clarke and had a half chance against Margetson.
1 min: Clarke charged down a chance for Chesterfield who came forward upon kickoff. Booty's left footed shot moments later was collected by Margetson.
Lou Macari rang the changes in the team to face Chesterfield. Kenny Irons, Delroy Facey and Gareth Evans came in while Adrian Moses, Thomas Heary and Chris Hay made way.