Dylan Hartley became the first player to be sent off in a Premiership final as Saints suffered a 37-17 defeat at the hands of Leicester Tigers at Twickenham.
The Northampton skipper was dismissed on the stroke of half-time for swearing at referee Wayne Barnes.
And, inevitably, it proved to be a huge blow to Saints’ chances of success as they could not recover from a 16-5 half-time deficit.
A try from Niall Morris and points from the boots of Toby Flood and his replacement George Ford, who came on for his injured captain on 23 minutes, put Tigers in control.
Stephen Myler’s score had kept Saints in the game but despite a hugely determined second-half display, they could not get their noses in front.
Instead, after impressive full-back Ben Foden had gone over to reduce the arrears to just seven points, tries from Graham Kitchener, Manu Tuilagi and Vereniki Goneva finished the game.
It was so tough on Saints, who showed the sort of spirit that had become their trademark during the season.
But for Tigers it was a first win in three finals as they made it eight successive wins against Jim Mallinder’s men to pick up the silverware.
Saints had gone into the game as big underdogs, despite their fine semi-final win at Saracens, but they displayed plenty of quality throughout.
Leicester had started with a bang as they flew into a 10-0 lead early on through Morris’s score and five points from Flood.
Saints needed a response and got it, as Lee Dickson’s quick tap from a penalty sent the ball out to Luther Burrell, who found Myler to dot down.
The fly-half missed the kick, but finally Mallinder’s men had a foothold in the game and they were upping their intensity minute by minute.
Courtney Lawes was an example of the increased drive and desire as he flattened Flood twice, the first hit bringing outrage from Richard Cockerill.
The Tigers boss was sent off for complaining about the tackle, which he felt was late, and Ben Youngs missed the penalty attempt with Flood recovering from treatment.
The No.10 was soon forced off, though, being replaced by Ford, before Saints spurned a good try-scoring opportunity as Foden failed to find the final pass.
Ford put Tigers eight points up before the break, kicking a penalty which was won after a rapid break from his own half by Matt Tait.
In the battle of the full-backs, Foden tried to respond, flying over the line but fine work from Graham Kitchener ensured the Saints man was in touch when he grounded the ball.
The men in blue had exerted the pressure, but they were being made to pay for their profligacy.
The teams looked set to go in at half-time separated by eight points, but a bizarre turn of events ended Saints’ chances of victory.
With time up, Myler was told not to kick the ball out by referee Barnes, but the fly-half did anyway, leading to a Leicester scrum.
Saints skipper Hartley then failed to heed a warning about back-chatting and after swearing at Barnes was shown a red card.
Ford kicked the penalty to make it 16-5 and leave Northampton with a mountain to climb, 11 points down and without their captain for the entire second half.
But Saints emerged with a point to prove and a fight to cause, exactly what they relish and Foden had the bit between his teeth as he finished off a fine move.
Myler missed the conversion to leave Tigers 16-10 ahead and Cockerill’s men soon restored their 11-point advantage as Kitchener beat the defence to score.
Ford fluffed the conversion from out wide, but he made a better job of a penalty soon after to put Tigers 24-10 up.
Still Saints wouldn’t lie down, though, as a brilliant run from Burrell saw him offload to Dickson to score.
Myler converted and his side were back to within seven points. It was a sterling effort from a team shorn of its skipper.
The Northampton fans responded to the grit being shown by their side, cajolling the players forward at every opportunity.
But hearts were about to be broken as, with 13 minutes left on the clock, Tuilagi landed the hammer blow, surging through the Saints defence to score.
Ford missed the kick once more, but his team were 12 points in front with time ticking away.
And it wasn’t long before Goneva put the seal on proceedings, touching down with Saints desperately trying to keep up with him.
The loss of their captain had, ultimately, ruined Saints’ hopes of victory, but their determination to succeed will stand them in good stead for a renewed push next season.
Saints: Foden (G Pisi 68); K Pisi, Wilson, Burrell, Elliott (Haywood 40); Myler (Lamb 68), Dickson (Roberts 68); Tonga’uiha (A Waller 54), Hartley (c), Mujati (Mercey 56); Lawes, Day (van Velze 60); Dowson (Nutley 68), Wood, Manoa.
Leicester: Tait; Morris, Tuilagi, Allen, Goneva (Smith 75); Flood (c) (Ford 23), B Youngs (Harrison 75); Mulipola (Balmain 75), T Youngs (Hawkins 68), Cole (Castrogiovanni 68); Kitchener (Slater 54), Parling; Croft, Salvi, Crane (Mafi 75).