Plymouth goalkeeper Jake Cole condemned his side to defeat with a second-half blunder as Northampton stayed in the thick of the promotion picture.
Cole fumbled a corner under pressure from Cobblers skipper Kelvin Langmead, allowing Clive Platt to force home.
It spoiled an otherwise competent display which saw him save from Roy O'Donovan, Harding and Bayo Akinfenwa.
Former Northampton defender Anthony Charles had a late chance to snatch a point but headed wide from a corner.
VIEWS FROM THE DRESSING ROOM
Northampton Town manager Aidy Boothroyd tells BBC Radio Northampton:
"We were made to scrap for it. We didn't play very well today, but it's about winning.
"Only Lee Collins and Roy O'Donovan played up to their normal levels and the rest were a tad below par, but that's how it is sometimes.
"There was a bit of fortune with the goal, but we didn't get very much fortune at AFC Wimbledon, so it's evened itself out.
"Everyone has their favourites on team selection, but it's me who picks the team. At times today, we looked good, but we know we can play better."
Plymouth Argyle manager John Sheridan told BBC Radio Devon:
"It was a ridiculous goal. I'll go in and see the referee and I'll ask him the question 'Who scored the goal?'.
"It was a clear foul on the keeper and it's only the ref that doesn't see it.
"But he's probably never played football so he won't have seen what the foul was. Get ex-players in officiating who know the game.
"We're in a scrap but we have to be realistic. We have to look at how we're going to create more chances and score goals to win games."
Live Text Commentary
Full Time The final whistle is blown by the referee.90:00 +3:00
Maxime Blanchard gives away a free kick for an unfair challenge on Roy O'Donovan. Roy O'Donovan restarts play with the free kick.90:00 +0:38
Free kick awarded for a foul by Gozie Ugwu on Kelvin Langmead. Free kick taken by Lee Collins.90:00 +0:08
Shot by Jake Robinson from just outside the area goes over the net.88:56
Jason Banton crosses the ball.87:28
The ball is delivered by Ben Tozer, save made by Jake Cole.85:50
Lee Nicholls takes the direct free kick.85:50 Substitution
Substitution Jake Robinson on for Clive Platt.85:50
The offside flag is raised against Gozie Ugwu.85:03
Foul by Clive Platt on Conor Hourihane, free kick awarded. Conor Hourihane takes the direct free kick.84:53
Centre by Ben Tozer, clearance made by Onismor Bhasera.83:02
Corner from the left by-line taken by Jason Banton, Close range headed effort by Anthony Charles misses to the right of the goal.80:55 Substitution
Substitution Reuben Reid goes off and Ronan Murray comes on.80:25
Effort from deep inside the area by Adebayo Akinfenwa clears the bar.76:23 Substitution
Substitution Andres Gurrieri is brought on as a substitute for Paul Wotton.72:19 Substitution
Substitution (Plymouth) makes a substitution, with Gozie Ugwu coming on for Paris Cowan-Hall.72:19 Booking
Booking Paul Wotton is cautioned.71:15
The assist for the goal came from Ben Harding.71:15 Goal scored
Goal! - Clive Platt - Northamp'n 1 - 0 Plymouth A goal is scored by Clive Platt from close in low into the middle of the goal. Northampton 1-0 Plymouth.69:46
Corner taken by Ben Harding.
Adebayo Akinfenwa takes a shot. Jake Cole makes a save.68:25
Chris Hackett crosses the ball, save by Jake Cole.67:37
Onismor Bhasera challenges Chris Hackett unfairly and gives away a free kick. Free kick taken by Ben Tozer.66:16
Anthony Charles gives away a free kick for an unfair challenge on Adebayo Akinfenwa. Lewis Hornby takes the free kick.65:41
Adebayo Akinfenwa concedes a free kick for a foul on Anthony Charles. Jake Cole restarts play with the free kick.64:20
Ben Harding concedes a free kick for a foul on Paul Wotton. Guy Branston takes the free kick.63:24
Unfair challenge on Adebayo Akinfenwa by Reuben Reid results in a free kick. Direct free kick taken by Lee Nicholls.62:48
Lewis Hornby gives away a free kick for an unfair challenge on Paris Cowan-Hall. Direct free kick taken by Conor Hourihane.61:56
Corner taken right-footed by Lee Collins, save made by Jake Cole.61:33
Maxime Blanchard concedes a free kick for a foul on Chris Hackett. Free kick taken by Chris Hackett.60:26
Centre by Chris Hackett.60:01
Roy O'Donovan produces a curled right-footed shot from 20 yards. Anthony Charles gets a block in.59:08 Substitution
Substitution John Johnson goes off and Adebayo Akinfenwa comes on.58:33
Headed effort from inside the area by Clarke Carlisle misses to the right of the goal.56:38
Chris Hackett concedes a free kick for a foul on Jason Banton. Direct free kick taken by Jake Cole.56:17
Foul by Reuben Reid on Clarke Carlisle, free kick awarded. Kelvin Langmead takes the free kick.55:08
Corner taken right-footed by Chris Hackett from the left by-line, Jake Cole fouled by Clive Platt, the ref awards a free kick. Free kick taken by Jake Cole.54:17
Free kick awarded for a foul by Conor Hourihane on John Johnson. Free kick taken by Ben Harding.52:47
Onismor Bhasera takes a shot. Comfortable save by Lee Nicholls.52:26
Short corner taken by Jason Banton.51:18
Effort on goal by Lewis Hornby from 20 yards. Blocked by Guy Branston.50:31
The referee blows for offside against Reuben Reid. Lee Nicholls takes the free kick.49:42
Reuben Reid is flagged offside by the assistant referee. Lee Nicholls takes the free kick.49:21
The assistant referee signals for offside against Chris Hackett. Free kick taken by Jake Cole.49:06
The referee gives a free kick against Maxime Blanchard for handball. Free kick taken by Kelvin Langmead.48:29
Kelvin Langmead gives away a free kick for an unfair challenge on Reuben Reid. Conor Hourihane takes the free kick.47:21
Guy Branston concedes a free kick for a foul on Clive Platt. Direct effort from the free kick comes in from Chris Hackett, Jake Cole makes a save.46:21
The ball is swung over by Chris Hackett, Header by Roy O'Donovan from deep inside the penalty area misses to the left of the target.45:01
The second half begins.45:00 +1:28 Half time
Half Time The half-time whistle blows.44:42
Lee Collins challenges Paris Cowan-Hall unfairly and gives away a free kick. Conor Hourihane restarts play with the free kick.40:38
Conor Hourihane produces a cross, Anthony Charles takes a shot. Save by Lee Nicholls.40:15
Inswinging corner taken left-footed by Jason Banton, clearance made by Clive Platt.38:55
Clive Platt challenges Paul Wotton unfairly and gives away a free kick. Jake Cole restarts play with the free kick.38:18
The official flags Reuben Reid offside. Indirect free kick taken by Lee Nicholls.36:58
The referee gives a free kick against Paris Cowan-Hall for handball. Free kick taken by Lee Nicholls.35:09
Chris Hackett fouled by Conor Hourihane, the ref awards a free kick. Lee Nicholls restarts play with the free kick.33:45
Shot comes in from Ben Harding from the free kick, save by Jake Cole.33:45 Booking
Booking Onismor Bhasera is shown a yellow card for unsporting behaviour.33:34
Onismor Bhasera challenges Roy O'Donovan unfairly and gives away a free kick.33:06
Paris Cowan-Hall sends in a cross, Clarke Carlisle manages to make a clearance.31:08
Paul Wotton takes a shot and went wide right of the net.30:33
Shot by Jason Banton. Kelvin Langmead gets a block in.29:00
Chris Hackett has an effort at goal from outside the box which goes wide right of the target.28:20
Paul Wotton concedes a free kick for a foul on Clive Platt. Direct free kick taken by Ben Tozer.26:23
Kelvin Langmead fouled by Reuben Reid, the ref awards a free kick. Direct free kick taken by Lee Nicholls.24:12
John Johnson gives away a free kick for an unfair challenge on Jason Banton. Onismor Bhasera takes the free kick.23:47
The ball is sent over by Maxime Blanchard, Kelvin Langmead makes a clearance.21:00
Ben Harding produces a right-footed shot from just outside the penalty area that goes harmlessly over the target.20:12
Ben Harding takes a shot. Blocked by Anthony Charles.18:23
Shot from 25 yards by Roy O'Donovan. Outswinging corner taken right-footed by Ben Harding, clearance by Conor Hourihane. Clearance by Paris Cowan-Hall.16:05
Lee Cox fouled by Kelvin Langmead, the ref awards a free kick. Conor Hourihane sends in a cross, Headed effort from deep inside the area by Guy Branston misses to the right of the goal.13:15
Kelvin Langmead challenges Reuben Reid unfairly and gives away a free kick. Free kick taken by Conor Hourihane.11:37
Jason Banton delivers the ball, Lee Nicholls makes a save.10:43
Paul Wotton fouled by Clive Platt, the ref awards a free kick. Free kick taken by Jake Cole.10:34
Reuben Reid is ruled offside. Lee Nicholls takes the free kick.8:38
A cross is delivered by Maxime Blanchard, Reuben Reid takes a shot. Kelvin Langmead gets a block in.6:32
Effort on goal by Jason Banton from 30 yards. John Johnson gets a block in.4:55
The ball is sent over by Maxime Blanchard, save by Lee Nicholls.3:56
The ball is swung over by Jason Banton.2:49
Jason Banton decides to take a short corner.0:42
Anthony Charles challenges Roy O'Donovan unfairly and gives away a free kick. Chris Hackett delivers the ball from the free kick right-footed from left wing.0:00
The referee gets the match started.
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