Northampton ran in 10 tries to beat Newcastle and seal a Premiership play-off spot for the first time since 2019.
Sam Matavesi, Alex Coles, Alex Mitchell and Tommy Freeman gave Saints a comfortable 36-7 half-time lead.
Falcons replied with a penalty try after Mitchell was sin-binned, as Jamie Blamire and Adam Radwan also scored.
But Newcastle had Sean Robinson sent off for head contact as Rory Hutchinson touched down, with Freeman completing a hat-trick late on to make it 65-26.
Northampton's victory wraps up a fourth-place finish and means they will travel to face leaders Leicester Tigers in their play-off next Saturday.
Dan Biggar's penalty got Saints off the mark and came after some good work from Matavesi and Fraser Dingwall, with the former gathering a loose Falcons pass to cross over.
Coles once again prospered from some good work from Dingwall to send them further ahead, with Matavesi powering over for his second.
Callum Chick hit back for Newcastle's first points on the board but Mitchell and Freeman both touched down to conclude a sensational first-half performance.
Not to be outdone, Falcons stormed out of the blocks on the restart, and after they were rewarded with a penalty try for side-entry at the maul, a sensational cross-field move set up Radwan's score.
Newcastle's fine start to the second half ended soon after, however, as Robinson saw red for making contact with Biggar's head in the build-up to Hutchinson's try.
Freeman wrapped up his hat-trick with two quickfire tries before Courtnall Skosan and Lewis Ludlam, scoring on his 100th Saints appearance, ensured a first home win against the Falcons in their past four meetings and wrapped up a play-off spot in style.
Northampton Saints director of rugby Chris Boyd:
"The danger of a game like this, where you know that trying to win the game is so important to get that fourth spot, you invariably push too hard to try things.
"We knew that if we went forward and created platforms to work off, we'd probably get enough platforms to get a few tries, but we tried to force things too much.
"There's probably not much out of that you take into Leicester. Stakes are high, obviously, but it will be a completely different game.
"To be fair, two months ago I think we were sitting eighth or ninth and a long way away from looking fourth.
"We talked about the fact we were probably playing knock-out football and we've managed to just sneak into that top four."
Newcastle director of rugby Dean Richards:
"The red card didn't help much at all - it was probably the turning point for us.
"Having said that, I thought their nine and 10 were outstanding and when they lost their nine [Mitchell] to a yellow card, that sort of hampered them quite a bit.
"On the day, I thought they were probably two or three scores better than us and when you're chasing a game and you get within a few points, as we did, sometimes you've got to tighten things up and we didn't.
"We carried on playing and that loose way, even when we were down to 14 men, sometimes it can come back to haunt you a little bit. But full credit to the boys; I thought they stuck at it."
Northampton: Furbank; Proctor, Dingwall, Hutchinson, Freeman; Biggar, Mitchell; Waller, Matavesi, Hill, Coles, Ratuniyarawa, Lawes, Hinkley, Ludlam (capt).
Replacements: Haywood, Iyogun, Painter, Ribbans, Nansen, Augustus, James, Skosan.
Sin-bin: Mitchell (47).
Newcastle: Tait; Radwan, Orlando, Burrell, Carreras; Hodgson, Young; Brocklebank, McGuigan, Davison, Peterson, Robinson, Graham, Basham, Chick (capt).
Replacements: Blamire, Mulipola, Kenny, Merrick, Fearns, Nordli-Kelemeti, Haydon-Wood, Wacoke.
Sin-bin: Peterson (40).
Sending-off: Robinson (59).