Catalans Dragons produced a sensational performance to hammer St Helens 35-16 and book their place in the Challenge Cup final in one of the biggest shocks in the competition's recent history.
Saints finished Super League's regular season 10 points clear of the rest but they had no answer to the inspired Dragons as the French side reached Wembley for only the second time.
Catalans coach Steve McNamara urged his players to seize the moment with the club's first silverware in sight and they responded in a remarkably one-sided opening 40 minutes.
St Helens were already rocking when Morgan Knowles was sin-binned and the Dragons went for the kill with the forward off the field, scoring two tries through Tony Gigot and Ben Garcia to take a stunning 27-0 lead into half-time.
Saints came out firing in the second half but their decade-long wait to get their hands on the Challenge Cup goes on despite Mark Percival's double and a try from Louie McCarthy-Scarsbrook.
The result was as unexpected as the only previous time the Dragons reached Wembley in 2007 with victory over Wigan.
On that occasion St Helens were far too strong in the showpiece as they secured the second of a hat-trick of Challenge Cups, but Catalans turned the tables in Sunday's double-header at Bolton.
There was little sign of the drama to come when prop Luke Thompson made a rampaging break in the opening minutes.
But the attack came to nothing and it was Catalans who posted the first points through Josh Drinkwater's penalty from in front of the sticks.
Super League's runaway leaders St Helens struggled for any kind of rhythm in the first quarter as the Dragons grew in confidence.
That belief was evident when they turned down the offer of another two points from a penalty and went in search of the game's opening try, which they duly claimed through Lewis Tierney's flying finish in the corner.
Drinkwater added the extras from the touchline to make it 8-0 and things continued to go the French outfit's way as James Roby lost the ball over the line at the end of Saints' best attack of the half.
It proved to be only brief hope for the St Helens fans as the Dragons took control in ruthless fashion as half-time approached.
Drinkwater's delayed short ball put Garcia over from close range before Gigot caught Saints napping with a cheeky drop goal from right in front.
St Helens were still in the match at 13-0 but Knowles' yellow card proved to be the pivotal moment.
Drinkwater slotted over another two points after Knowles was penalised for a high tackle on Kenny Edwards and Gigot backed up Benjamin Jullien's break to score Catalans' third try.
Garcia piled more misery on Saints by cruising over out wide for his second and Drinkwater's third penalty just after the break made it 29-0.
The tie was over as a contest but St Helens did at least get on the board when Percival raced over in the corner after quick hands from Ben Barba.
Justin Holbrook's side hinted at an unlikely comeback after McCarthy-Scarsbrook powered his way over and Danny Richardson added his first goal of the afternoon.
But Sam Moa ran over the top of Theo Fages to score and put the result beyond any doubt, ensuring Percival's finish out wide was mere consolation for the shell-shocked Saints.