Leicester reached their first Premiership final for nine years after George Ford inspired an intense 27-14 victory over Northampton at Mattioli Woods Welford Road.
Tigers, who extended their unbeaten home record in English rugby's flagship domestic competition to more than a year, were given a major examination by their east midlands rivals throughout an emotion-charged play-off with Ford scoring 22 points.
A minute's applause took place before kick-off in memory of Tiffany Youngs, whose husband Tom retired in April following a career that saw him captain the club and make more than 200 first-team appearances.
Tom's brother, England scrum-half Ben Youngs, started for Leicester as Tigers booked a Twickenham appointment with Saracens next Saturday.
Ford, on his final Leicester home appearance before joining Sale later this summer, contributed a try, conversion, four penalties and a drop-goal, and delivered a scoring pass for Freddie Steward's clinching late touchdown.
Saints replied through a Tommy Freeman touchdown, with Dan Biggar kicking two penalties and James Grayson one but Wales international Biggar went off early in the second period after appearing to suffer a knock.
But ultimately, it was Leicester's day, setting up a pulsating finale when they will go in search of a ninth Premiership title.
Hooker Julian Montoya and centre Dan Kelly returned to the Leicester starting line-up, while Northampton changes included Freeman switching to full-back instead of an unavailable George Furbank, with number eight Juarno Augustus also featuring.
Kelly, though, limped off after just three minutes, causing a back division reshuffle as Guy Porter moved into midfield, replacement Freddie Burns lined up at full-back and Steward switched to the wing.
Biggar then kicked Northampton into the lead, landing a 48-metre penalty after seven minutes before Saints full-back Freeman launched a thrilling counter-attack that ended with him being bundled into touch.
Saints were comfortably the more dangerous team early on, and they were denied an Alex Mitchell try after wing Courtnall Skosan knocked on, before Skosan spilled a pass when a clear run to the line beckoned.
Leicester's response to an unsettling opening quarter was to set up camp in the Northampton 22, helped by a wild Augustus pass that allowed them an attacking lineout.
Ford tied things up through a short-range penalty, but Skosan's horrors continued after Saints centre Rory Hutchinson burst clear in midfield, only for the South African to waste another clear-cut chance by dropping the ball.
A second Ford penalty edged Tigers ahead seven minutes before the break, just as Biggar received treatment after seemingly taking a blow to his back.
Saints ended the half back in the driving seat, and Biggar's second penalty made it 6-6 at the break after Porter was yellow-carded for a high tackle on Hutchinson.
With Porter still off, Northampton deservedly took the lead following sustained pressure that asked many questions of Leicester's defence.
And Freeman had an easy finish as Leicester ran out of numbers, as Biggar's missed conversion was his final contribution before leaving the action and being replaced by Grayson.
Leicester were in trouble again, yet they managed to conjure a response this time as Ford weaved his way through Northampton's defence for a try that he also converted.
Grayson sent an angled penalty chance wide after Skosan was tackled in the corner, only to make amends four minutes later as Saints edged back in front.
But when replacement Northampton prop Oisin Heffernan was sin-binned for a high challenge on Jasper Wiese, Leicester looked to make it count.
Ford, inevitably, delivered the goods after kicking an earlier penalty as Leicester attacked at pace, and his floated delivery found an unmarked Steward, who finished off to finally floor Saints and secure a trip to Twickenham that was sealed by Ford's drop-goal and another penalty.