AA slick, destructive performance by promotion-chasing Mansfield broke the Cobblers hearts.
The Stags are the country's leading scorers and have now hit 20 in their last 6 matches. Finishing power was the difference against a Northampton side whose final ball frequently let them down.
Northampton could hardly afford to shoot themselves in the foot in the way they gifted Mansfield a fourth minute lead. But a sloppy back pass by Des Lyttle hit Ian Sampson on the foot and fell kindly for Iyseden Christie who made no mistake.
Visiting goalkeeper Kevin Pilkington was a virtual spectator, hardly making a significant save in the whole match and Lee Williamson could have stretched the visitors lead at the other end only to fire wide after a surging run, while a second blunder from Lyttle almost let Christie in once more.
Mansfield stretched their lead in the 65th minute when their pace on the counter attack again caused the problems, and this time Junior Mendes was tripped from behind by Christopher Willmott to give them a penalty which Liam Lawrence converted for his tenth goal of the season.
The points were sealed ten minutes from time when a poor clearance by Luke Chambers was seized upon by Williamson and his low cross was touched home at the far post by Craig Disley.
Stags boss Keith Curle said; "This is one more step along the journey which I have spoken about. To say I am delighted with the result today is an understatement.
"The one thing we have got in this side is pace. We made tactical changes today with Craig Disley coming in to counter the attacking threat of Josh Low. We also had Tom Curtis as a 'sitting' midfield player, but every time I looked up he was in their box."