A Stephen Myler drop goal five minutes from time took Northampton to the final of the European Challenge Cup on Friday, with a 16-13 win over Saracens.
The scores were level at 13-13 in a tensely-fought semi-final when Myler struck to earn Saints a final place against Worcester or French side Bourgoin.
Northampton had opened up a 13-3 half-time lead with a try from skipper Bruce Reihana and two penalties and a conversion from Myler.
But Saracens hit back in the second half to draw level with winger Rod Penney going over and Glen Jackson, this season's Guinness Premiership leading points scorer, adding a penalty and a conversion to his first-half penalty.
The stakes were high with Europe's second-tier knockout competition providing the last chance for both clubs to qualify for next season's Heineken Cup.
The early desire boiled over with a scuffle, involving around 10 players from each side, ending with French referee Romain Poite calling out rival captains Steve Borthwick and Reihana to issue a general warning with only 44 seconds on the clock.
England captain Borthwick was involved again 10 minutes later when he intervened to pull Northampton's England hooker Dylan Hartley away from a grappling match with Penney.
Jackson had kicked Saracens ahead with a fourth-minute penalty form close range but Myler equalised three minutes later.
Former league player Myler kicked Northampton ahead in the 13th minute after their scrum forced the back-pedalling Saracens pack to concede a penalty just inside their own half.
The fast-moving Saints attack, spearheaded by dangermen Reihana and full-back Ben Foden, was causing problems for the visitors.
But Saracens, defending well, denied Northampton an opening try when a move, in which Myler figured twice, ended with Foden edged into touch as he tried to put a return pass back inside to his skipper.
When the rival packs clashed again after the next scrum collapsed in the 29th minute the French official despatched both hookers, Hartley and Saracens' Fabio Ongaro, to the sin bin for 10 minutes.
Replacements Brett Sharman and Matt Cairns were called from the bench as a temporary measure before Northampton won the reset scrum but Saracens turned over possession to clear their lines after surviving a lengthy spell of pressure.
The relief was short-lived as Saints came again with heavyweight Tongan prop Soane Tonga'uiha's barnstorming run taking him to within a couple of yards of the try line.
Saracens, continuing to resist, repelled three forward drives before Northampton moved the ball wide with right wing Paul Diggin and centre Jon Clarke combining before Clarke's long pass sent the unmarked Reihana over in the left corner in the 29th minute, with Myler converting from out wide.
The home side almost scored again on the stroke of half-time when Diggin hacked on after a pass from Jackson, went to ground and dived on the loose ball but the referee called up the video official who ruled that he had touched down on the dead ball line.
Jackson's second penalty reduced the deficit to seven points in the 51st minute after the Saracens pack dominated their counterparts at the breakdown, forcing them to offend.
Saracens introduced former Great Britain rugby league captain Andy Farrell, playing the final match of his illustrious dual-code career before heading into retirement, and they proved much more of a threat in the second half.
Farrell twice drove hard at the heart of the Northampton defence, wingers Noah Cato and Penney both threatened and centre Brad Barritt had Northampton scrambling to clean up when he chased his own kick after the home side spilled possession.
American full-back Chris Wyles went closest when he was bundled into touch a metre short of the Northampton line.
The Saints brought on 37-year-old former Scotland prop Tom Smith in the 69th minute for the final time at Franklin's Gardens before he retires - but he could still be wheeled out one more time for the final.
The home side's defensive resilience finally cracked in the 73rd minute when Saracens centre Adam Powell sent Penney in down the right and Jackson converted to level the scores.
But, with the match seemingly heading for extra time, Saints came again to set up the chance for Myler to land his coolly-taken winning drop goal from nearly 40 metres out in the 75th minute and they maintained the pressure to deny Saracens any chance to retaliate.
Pens: Myler 2
Drop goal: Myler
Pens: Jackson 2
Northampton: 15 Ben Foden, 14 Paul Diggin, 13 Jon Clarke, 12 James Downey, 11 Bruce Reihana (capt), 10 Stephen Myler, 9 Lee Dickson, 8 Mark Easter, 7 Scott Gray, 6 Neil Best, 5 Juandre Kruger, 4 Ignacio Fernandez Lobbe, 3 Euan Murray, 2 Dylan Hartley, 1 Soane Tonga'uiha.
Replacements: 16 Brett Sharman, 17 Tom Smith, 18 Courtney Lawes, 19 Mark Hopley, 20 Alan Dickens, 21 Barry Everitt, 22 Joe Ansbro.
Saracens: 15 Chris Wyles, 14 Rodd Penney, 13 Francisco Leonelli, 12 Brad Barritt, 11 Noah Cato, 10 Glen Jackson, 9 Neil de Kock, 8 Ben Skirving, 7 Dave Seymour, 6 Chris Jack, 5 Tom Ryder, 4 Steve Borthwick, 3 Census Johnston, 2 Fabio Ongaro, 1 Matias Aguero.
Replacements: 16 Matt Cairns, 17 Tom Mercey, 18 Hugh Vyvyan, 19 Andy Saull, 20 Mickey Wilson, 21 Andy Farrell, 22 Andy Powell.
Referee: Romain Poite (France)
Television match official: Christophe Berdos (France)