Wycombe substitute Stuart Roberts struck a second-half hat-trick to condemn Northampton to a humiliating 5-0 defeat at Sixfields.
Jonny Dixon (8) shot Wycombe ahead but Northampton should have at least been on level terms by the break.
Frank Tallia twice denied Marco Gabbadiani, who also glanced a header wide, while Darryn Stamp was just off target with a header and hooked another shot over the bar.
They were made to pay when Wycombe doubled their lead on the stroke of half-time as Michael Simpson's free kick deceived everyone in the box and ended up in the net.
Straight from the re-start Roberts cut into the box to slot the third before adding his second in the 79th minute after racing clear.
And three minutes later the super-sub completed his hat-trick after a smart turn in the area.