A Charlie Raglan first half header and a late goal by Conor Thomas handed Cheltenham Town a useful advantage after tonight's first leg of the play-off semi-finals.
The goals capped an impressive performance at an eerie PTS Academy Stadium, although they didn't have it all their own way and a string of fine saves by Owen Evans kept Michael Duff's side in it ahead of the return fixture in four days' time.
The big moment in this one arrived in the opening exchanges when Evans brilliantly saved a penalty, nine minutes before the opening goal at the other end.
The Robins combined some sublime football with resillient defending to restrict the Cobblers over the course of the evening before finding the late goal to cap a satisfying evening's work.
There were three changes to the side that last turned out 103 days ago with Duff partnering strikers Reuben Reid and Tom Nichols, who had previously only made one start.
The early drama arrived with 16 minutes on the clock when the home side were handed the spot kick. Ryan Broom had brought down Michael Harriman to concede a penalty after the game had been held up for several minutes due to an injury to assistant referee Alan Clayton.
It handed Ryan Watson the opportunity to put his side in front but Evans guessed correctly, diving to his right to produce a fine save to keep the Robins in it.
Nine minutes later they were in front through Raglan who met a Jake Doyle-Hayes corner with a firm header to open the scoring with his second goal of the campaign.
Cheltenham produced some fantastic football at times and Reid went one to force Steve Arnold into a low save as they searched for a second.
The Cobblers though finished the half strongly and called Evans into a couple of smart saves before James Olayinka produced a brilliant piece of skill to force the Robins number one into a flying stop deep into added on time.
There was some more defending to do at the start of the second half. Evans came to the rescue again to deny Callum Morton, who was found in an acre of space by Olayinka from the left. However the striker was ponderous and Evans took advantage, diving at his feet to clear the danger.
Scott Wharton then met cross by Nicky Adams but his header flew wide.
At the other end Nichols curled one high and wide of the target and Reid went close, cutting in from the right before firing one straight at Arnold, who pushed away the effort.
Keith Curle made a double change 23 minutes from time, sending on former youth striker Andy Williams and Paul Anderson to replace Callum Morton and Alan McCormack.
Moments later Duff made one of his own, swapping his forward line to press Alfie May and Jonte Smith into action for the final 16 minutes of the contest.
Olayinka was a whisker away from notching the equaliser, shaving the bar with a firmly hit effort from the edge of the box.
But the Robins dealt a major blow to Northampton's hopes of salvaging a result when Thomas slotted home four minutes from time.
Evans pumped a long ball forward to start the move involving Thomas, Hussey and Smith, teeing up Sean Long for an angled effort down the right. The low effort was parried into the path of the midfielder who did the rest from 12 yards to notch his seventh goal of the campaign and put Duff's side in the driving seat for the return tie in four days time.
NORTHAMPTON TOWN (3-5-2): Arnold; Goode (c) (Anderson 67), Turnbull, Wharton; Harriman, Watson, McCormack, Olayinka, Adams; Morton (Williams 67), Oliver (Smith 76). Subs not used: Cornell (Gk), Martin, Smith, Pollock, Lines, Roberts, Anderson, Marshall.
CHELTENHAM TOWN (3-5-2): Evans; Raglan, Tozer (c), Boyle; Long, Thomas, Broom (Ince), Doyle-Hayes, Hussey; Reid (Smith 74), Nichols (May 74). Subs not used: Clements, Sheaf, Debayo, Lovett (Gk), Greaves, Varney.
REFEREE: M Edwards