Jonte Smith and his Cheltenham Town teammates surrendered their two-goal first-leg advantage on a hugely disappointing evening, costing them a trip to Wembley.
Smith started the match but was a half-time substitute.
Two second-half goals by Callum Morton put paid to the dream of a fourth major final at the national stadium next week.
Vadaine Oliver had given Northampton the perfect start with an early goal and it set the tone for a forgettable night with so little to cheer from a Cheltenham perspective.
Credit to Northampton Town for a spirited fightback but this was a calamitous evening for Michael Duff's side, who were quite simply second best all evening at an empty Jonny-Rocks Stadium.
