Stuart Roberts bagged a glorious hat-trick as Wycombe raced to their first away win in the league for three months.
Wanderers joy contrasted sharply with the misery suffered by Northampton, who have now lost their last four home matches without scoring a goal.
This defeat equalled their biggest-ever home loss at the Sixfields Stadium.
Roberts came on as a 33rd minute substitute for Johnny Dixon who had already fired the visitors ahead in the eighth minute after a neat move involving Steve Brown and Craig Faulconbridge.
The visitors made it 2-0 in the closing minute of the first half when Michael Simpson fired in a low free-kick which deceived Glyn Thompson in the home goal as bodies obscured his view.
The second half was the property of Welsh striker Roberts who made it 3-0 in less than 20 seconds after the re-start when he cut in from the left and drilled a low shot inside Thompson's near post.
Roberts made it 4-0 11 minutes from time when he latched on to another precision pass from playmaker Brown before beating Thompson, who was again picking the ball out of the net three minutes later.
This time Roberts latched on to a pass from Danny Senda before scoring.
Ironically Northampton bossed much of the first half and had enough chances to be ahead let alone facing a two-goal deficit.
Their leading scorer Marco Gabbiadini had four decent openings, glancing a seventh minute header wide from a Chris Marsh cross.
But his clearest chance came ten minutes before the break when he was put clear by Chris Hargreaves, but somehow managed to drag the ball wide.