Substitute Aaron Holloway scored a dramatic late equaliser in the eighth minute of time added on to give Wycombe a last-gasp 1-1 draw with the Cobblers.
Town had been in front for two-thirds of the contest after Ryan Cresswell had scored his first goal for the club with a powerful header.
But they were denied with the final play of the game after showing good resistance and finishing the contest with 10 men following a controversial sending-off for Gregor Robertson.
Robertson was shown a second yellow for what referee Pat Miller felt was time-wasting, although the full-back was waiting for a substitution to be made.
The match official will come in for intense scrutiny after his performance, with several players booked in the aftermath of Wycombe’s equaliser as both sets of players almost came to blows.
The first glimpse of goal for the Cobblers came in the 25th minute when Hackett, in typical style, found space for a right-wing cross that was was headed goalwards by Kaid Mohamed but taken under pressure by goalkeeper Matt Ingram under pressure from Lawson D’Ath.
D’Ath should have scored moments later when he dived to head a Hackett cross wildly over the bar despite no defenders being anywhere near him.
Hackett had been set free by an excellent pass from Joel Byrom on the run, and from his weaker right side.
But Cresswell punished them with a thumping header from a similar distance on the half-hour mark, making excellent contact from a swirling Byrom free-kick from deep that gave Ingram no chance.
The response from Wycombe was almost non-existent, with long balls into the box comfortably claimed by Jordan Archer, whose reading of such situations was exemplary.
They made a better start to the second half, with Paris Cowan-Hall delivering devilish cross from the left wing which Lee Collins had to clear from no more than two yards out.
Most of their attacking football came from deep areas, with the ball launched into the box from all kinds of angles but the visiting defenders had the measure of it.
Marc Richards, from an offside position, had a header well saved by Ingram and Ivan Toney headed wide from a similar area soon afterwards.
Peter Murphy had the ball in the back of the net 10 minutes from time when he nodded in after Jordan Archer had parried Paul Hayes’ header against the underside of his own bar.
The home players then wanted a penalty after Archer came out for a cross and clattered Hayes, who got to the ball first but headed it wide.
Robertson’s strange dismissal meant the Cobblers were forced to play the final five minutes of normal time with just 10 men.
They had nine temporarily when Ricky Ravenhill had to leave the field after receiving a head injury that left Cresswell with blood on his shirt.
Archer made an excellent save to keep out a Sam Wood shot deep into the time added on to added time for that injury and from the resulting corner, Holloway powered in a header to break Town hearts.
Wycombe: Ingram; Jombati, Pierre, Mawson, Jacobson; Cowan-Hall, Murphy, Scowen, Wood; Hayes, McClure
Subs: Holloway (for McClure 64)
Not used: Richardson, Lewis, Bloomfield, Craig, Kretzschmar, Walker
Cobblers: Archer; Tozer, Collins, Cresswell, Robertson; Hackett, Byrom, Ravenhill, Mohamed; D’Ath, Toney
Subs: Carter (for D’Ath 54), Richards (for Mohamed 66), O’Toole (for Toney 88)
Not used: Snedker, Langmead, Moyo, Warburton
Away fans: 801
Referee: Patrick Miller