Wigan battled through to their first Challenge Cup final in seven years, surviving a battering in the first half, striking to devastating effect in the second and holding off the Saints in the closing stages of the match.
Saints lost a third semi-final in a row. They contributed fully to a compelling spectacle but could not quite counter the strike power of players like Sam Tomkins and Josh Charnley. They were without the soon-to-leave Kyle Eastmond, who suffered a recurrence of a hamstring injury in training, while Wigan's most notable absentee was Gareth Hock, who was left out.
St Helens spent most of the first 15 minutes on the attack, without quite looking clinical enough to turn their pressure into points. Their best chance came when Francis Meli made a clean break in the left-centre channel but he threw an ill-judged pass to Jamie Foster, a little too hard, a little too high.
More surprising was the way in which Wigan failed to take the lead, two minutes later. The Saints prop James Graham was penalised for an obstruction and the Wigan winger Pat Richards, the most reliable kickerin the game, had a chance from right in front of the posts. Unaccountably, he missed.
There was no such mistake from Foster when he got his opportunity. Considering how little they have played together, Leon Pryce and Jonny Lomax were combining remarkably well at half-back for Saints. A jinking run from the latter drew an offside penalty that the young winger stroked over without fuss.
That looked as though it might be the only score of a first half low on points but high on crunching defence, but seven minutes before the break Wigan scored a try out of nothing. Charnley's acceleration from a standing start put him in the clear, only for him to be mown down by a tackle that was timed with typical precision by Paul Wellens.
Cruelly, the Saints full-back's effort counted for little as the ball went promptly to the other side of the pitch for George Carmont to score from Ryan Hoffman's pass. This time, Richards succeeded with the kick, from the touchline and into a swirling wind.
Both sides thought they had scored early in the second half, Saints when James Roby's exquisite pass released Lomax, only for him to be chopped down by a quite superb tackle from Thomas Leuluai. Wigan's near miss came when the video referee, Steve Ganson, found an obstruction to deny Sam Tomkins a sniping try.
There was no argument, though, about the try that put Wigan within sight of a trip to Wembley for the first time in 13 years. Joel Tomkins got his pass away perfectly to Charnley but the winger still had plenty to do, beating three defenders on his way to the line. Nor was the younger Tomkins to be kept without a try for very long. Three minutes later he ran at flagging tacklers and planted the ball over the line.
Saints had a flicker of hope when Meli held up his pass to put Foster over after 64 minutes. Five minutes later, the pair repeated the process and the game was very much alive. Richards missed a late penalty that would have clinched it, but Wigan held on and celebrated as you would expect of a team returning to their spiritual home.
Wigan: S Tomkins; Charnley, Carmont, J Tomkins, Richards; Finch, Deacon; Lima, Leuluai, Coley, Hansen, Hoffman, O'Loughlin. Substitutes used: McIlorum, Mossop, Farrell, Cross.
St Helens: Wellens; Makinson, Shenton, Meli, Foster; Pryce, Lomax; Graham, Roby, Puletua, Flannery, Soliola, Wilkin. Substitutes used: McCarthy-Scarsbrook, Moore, Clough, Gaskell.
Referee: R Silverwood (Mirfield).