The Wanderers produced a hugely dominant display as they beat Harlequins 46-27 to book a home Prem Rugby A League final at Franklin's Gardens.
Francois van Wyk, Charlie Clare, Nafi Tuitavake, Lewis Ludlam and Tom Collins all wrote their names on the scoresheet, with the Wanderers also securing a penalty try.
Harlequins were completely outgunned up front during the first half and though their replacements helped them to compete better after the break, the Wanderers had too much power and quality.
Northampton, the reigning champions, will now face Exeter Chiefs, who beat Newcastle in the other semi-final, in the showpiece at Franklin's Gardens next Monday evening (April 30, 7.30pm).
The Wanderers signalled their intent from the off against Quins, smashing the opposition in the scrum and then forcing them to frantically back-pedal from two lineouts, with the second resulting in a score for prop van Wyk.
James Grayson added the extras and it was the perfect start for the home side, but Quins quickly got on the board, with fly-half James Lang notching a penalty.
But it wasn't long before the Wanderers forwards did the hard work once again, with Harlequins unable to resist as they conceded another scrum penalty and another try from a lineout drive.
Hooker Clare was the scorer of the hosts' second, but Grayson missed the conversion to leave the gap at nine points.
That margin was only going to get bigger if Harlequins didn't sort things out up front, and so it proved as another lineout provided the platform for Collins to set up Tuitavake out wide.
Grayson converted to make it 19-3 but Harlequins finally managed to get some momentum and registered their first score through lock Josh Ibuanokpe.
Lang converted to take his team into double figures, but Grayson responded with a good penalty after the Wanderers won the battle at the breakdown.
The half-time interval did little to help Harlequins as they were again hammered up front, forcing referee Adam Leal to award a penalty try.
The away side then opted to change both of their props in a bid to stem the tide and it paid immediate dividends as they were awarded a penalty try of their own.
Ben Nutley paid the price for the Wanderers' persistent infringements in the build-up, with the Wanderers No.8 shown the yellow card.
But it didn't affect the home side as Grayson made a big tackle to win possession back and after some slick play, indefatigable flanker Ludlam finished smartly.
Grayson converted superbly from the touchline and the Wanderers looked to be moving out of sight, but Quins weren't going quietly and Ibuanokpe got his second score of the game to keep them in it.
However, Lang missed the conversion and Grayson quickly landed a well-struck penalty to put the gap at 17 points with the clock ticking down.
Quins were then reduced to 14 men for the remainder of the match as replacement scrum-half Dave Lewis saw yellow as he frantically tried to stop Ludlam, who had spotted space and charged into it.
The Wanderers wasted little time in making the most of their numerical advantage as some fast hands helped Collins to get his customary try.
Grayson converted and the Wanderers were waltzing towards next week's final.
Harlequins did have the final say thanks to a score from Henry Cheeseman, but Lang missed the conversion with the final kick of an entertaining game.
Wanderers: T Collins; Tuitavake, Dingwall, Stephenson (c) (Strachan 69), Pisi (Elliott 69); Grayson, Mitchell (Kessell 77); van Wyk (Trinder 71), Clare (Fish 77), Painter (M Collins 69); Moon, D Onojaife (Beesley 77); Ryan, Ludlam (Allman 77), Nutley.
Harlequins: Swiel (Murley 63); R Chisholm, Sloan, Cheeseman, Ibitoye; Lang, Waters (Lewis 69); Boyce (Lambert 45), Crumpton, Swainston (McNulty 55); Okafor (Flashman 63), Ibuankope; South (c), White, Lamb.
Referee: Adam Leal