Shaun Pearson’s 63rd-minute header set the Cobblers on their way to defeat at Grimsby Town and ended their interest in this season’s FA Cup.
In a game of few chances, centre-back Pearson powered home from 15 yards to put the home side in front at Blundell Park, with Paddy McLaughlin scoring an excellent second in injury-time to settle it 2-0.
It means Northampton have lost to non-League opposition in two of the past three seasons and is the latest miserable chapter in what has been a poor season so far.
Town fielded a curious line-up for the game with last week’s most influential attacking player Clive Platt dropped to the bench and Ian Morris back in the side in a free role behind Jacob Blyth.
Chris Hackett, identified by Grimsby manager Paul Hurst as Town’s one to watch, played down the right wing and delivered a couple of problematic crosses in the game’s opening minutes.
Grimsby, though, were on the front foot. Lennell John-Lewis wanted a free-kick after a coming-together with Mathias Doumbe and Scott Neilson was very lively down the left.
Morris himself had Northampton’s first good chance, flicking on a Hackett dead ball at the near post to force James McKeown into a two-handed save.
Scott Kerr sliced wide at the other end after a good piece of play down the left involving the home side’s full-back Aswad Thomas.
Ross Hannah was probably Grimsby’s best attacking player and forced a good save from Matt Duke after spinning Doumbe on the edge of the box 10 minutes into the second half.
Kevin Amankwaah then had to make a fine point-blank block to keep out a stinging Hannah shot on the volley.
The goal came on 63 minutes, Hatton swirling in a devilish free-kick that Pearson thumped home with a bullet-like accuracy and power.
With the comfort of the lead, Grimsby defended deep and allowed the Cobblers to have plenty of possession in midfield areas.
Not that they did much with it - Joe Widdowson and Morris both had a couple of shots saved by McKeown but nothing above the routine.
McLaughlin’s goal was a fine one, a slaloming run past both tiring centre-backs and a cool finish underneath Duke.
Moments later the final whistle was blown, on the game and on Northampton’s FA Cup season.
Grimsby: McKeown, Hatton, McDonald, Pearson, Thomas, Rodman, Disley, Kerr, Neilson, John-Lewis, Hannah
Subs: Colbeck (for Neilson 67), McLaughlin (for Hannah 89)
Not used: Doig, Cook, Bignot, Thanoj, Southwell
Cobblers: Duke, Amankwaah, Reid, Doumbe, Widdowson, Emerton, Ravenhill, Deegan, Morris, Hackett, Blyth
Subs: Platt (for Emerton 58), Norris (for Widdowson 85), Demontagnac (for Deegan 85)
Not used: Carter, Collins, Demontagnac, McNamara, Toney
Away fans: 259