The Cobblers played the part of unlikely lads to the full by springing this surprise on form side Barnsley.
Kevan Broadhurst's side played the last 49 minutes with ten men after club captain Ian Sampson was sent off for a foul on Bruce Dyer which brought the Tykes a penalty.
But goalkeeper Lee Harper enjoyed his crowning hour by flinging himself to his right to save Chris Lumsdon's penalty, and the Cobblers took inspiration from that.
Despite a gritty second-half defensive display, the home side still had the temerity to snatch a smash and grab winner through substitute Paul McGregor 16 minutes from time.
The goal arrived after a steady stream of Barnsley pressure, during which Harper performed further heroics. The pick of his saves was a blinding 61st minute reaction stop to prevent Paul Gibbs' fierce low drive beating him from 12 yards out.
McGregor's introduction 19 minutes from time prompted a shift in the balance of play and his goal only arrived after quickfire chances had been missed by the goalscorer and Paul Trollope.
The winner saw the Cobblers substitutes combine, with Chris Carruthers crossing from the left. The ball dropped to McGregor who had time to pick his spot and beat Andy Marriott with a low drive from 15 yards.
It was reward for Northampton after a nightmare eight days which had brough two defeats as well as the collapse of takeover talks involving international criminal lawyer Giovanni Di Stefano.
Barnsley had not been beaten since the opening day of the season and manager Steve Parkin confirmed he wanted his side to prove themselves more ruthless in future.
"We proved we can do that at Luton and must aim to achieve that week in week out," he said.
HASH(0x95f6648)