The Wanderers booked their place in the semi-finals of the Premiership Rugby Shield thanks to a 38-28 derby-day win against Leicester Tigers at sun-soaked Franklin's Gardens.
Two tries from Andrew Kellaway, plus further efforts from George Newman, Connor Tupai, Ken Pisi and Tui Uru got the job done for the back-to-back A League champions.
Leicester had led three times at the Gardens, but the Wanderers kept fighting and earned the result that ensured they finished second in the Northern Conference.
They will now travel to Exeter Chiefs of Saracens, who are currently first and second in the Southern Conference respectively, in the final four on Monday, May 6.
The Saints second string only needed a single point from the game against Leicester to qualify, but they ended up with five thanks to a strong second-half showing.
Tigers had led 21-14 at the break, but they were outgunned during the second 40 minutes as they left the Gardens with nothing.
Leicester had started strongly, winning a few early penalties and using them to provide a platform for an opening score as Clayton Blommetjies spotted a gap and raced in.
Tom Hardwick added the extras, but the Wanderers responded strongly, winning a scrum penalty and launching an attack that Tigers couldn't stop.
James Grayson pulled the strings superbly, flinging a lovely lofted pass out to the left, where Kellaway, lining up at outside centre, did the rest.
Grayson converted from the touchline and the scores were level after a lively start.
But Leicester were looking a threat with ball in hand and after some tidy play, full-back Freddie Steward offloaded impressively for Blommetjies to score his second.
Hardwick converted from wide left and Leicester led by seven points again.
But the Wanderers were bossing the forward battle, winning a couple of penalties at the scrum before pushing Leicester over from a big lineout drive.
Hooker Newman was the man who profited to score, and Grayson converted impressively from out wide once again.
But Tigers then turned the tables in the scrum, winning a series of decisions from referee Fergus Kirby as the Wanderers found themselves under real pressure near their own line.
After another scrum motored towards the try line, looking like it might bring a penalty try, No.8 Fred Tuilagi collected the ball and scored.
Hardwick converted to put his team ahead for the third time in a topsy-turvy encounter, but again the Wanderers threatened to respond, with Mitch Eadie looking lively.
Tom Collins almost cut that gap just after the restart but he lost the ball under pressure while trying to score in the corner.
However, it wasn't long before the Wanderers had their third try as great build-up play from Collins and Tom Emery opened the door for Tupai to score.
Grayson sent the conversion just to the right of the right post, but the Wanderers finally led for the first time when they masterminded a brilliant bonus-point try.
Emery used the outside of his boot to kick ahead for Kellaway to gather and the Australian back offloaded from the ground for the onrushing Pisi to score.
Grayson converted to make it 26-21 and the Wanderers were heading for the semi-finals with at least a point now guaranteed.
Leicester started to really lose their way and the Wanderers were opening them up at will.
Kellaway scored his second after Emery took a huge hit to give the offload, and replacement No.8 Uru then etched his name on the scoresheet by charging in on the right.
Blommetjies completed his hat-trick for Tigers, with Hardwick converting, but it was too little, too late for the away side.
Wanderers: Emery (Worley 67); Pisi, Kellaway (Freeman 65), Strachan, Collins; Grayson (c),Tupai (Davies 67); Trinder (Davis 55), Newman (Taylor 70), Garside (Ford-Robinson 55); Jubb, Bean; Coles, Onojaife, Eadie (Uru 40).
Leicester Tigers: Steward; Gilliland, Creed, Bitirim, Blommetjies; Hardwick, Law; Ma'afu, McMillan, Cortes; Gray, Mapapalangi; Reffell, Evans (c), Tuilagi.
Replacements: Harding, Dimen, Feao, Smith, Kalamafoni, Findlay, Costelow, Veainu.
Referee: Fergus Kirby