Luke Gale’s golden point drop-goal broke Saints’ hearts as Castleford made it through to Super League’s Grand Final in an incredible match.
Returning to the side just 16 days after having his appendix removed, the England scrum-half scored a try and kicked four goals to put his side into a what appeared to be a winning 20-10 lead after 64 minutes.
However, in a dramatic finish to an outstanding semi-final, Saints roared back with three tries in the last 10 minutes to edge in front before Gale kept his nerve to kick a last-minute penalty to send the game into golden-point extra-time.
He then demonstrated more composure to land the winning drop goal that earned his side a 23-22 victory that set up a first all-Yorkshire final for 12 years.
Castleford, who will meet the winners of the Friday’s semi-final between Leeds and Hull at Old Trafford on October 7, have become the seventh club to reach a Grand Final and will be favourites to become only the fifth team to win a title held by just four teams in the 21 years of Super League.
The Tigers were universally acknowledged as by far and away the best team in the league in 2017, finishing 17 points ahead of their fourth-placed opponents, but St Helens deserve enormous credit for their part in a remarkable game in which they outscored their hosts by five tries to three.
Saints could hardly have made a worst start, with second rower Zeb Taia knocking on from the kick-off and Castleford full-back Zak Hardaker scored from the resultant scrum after Gale had handled twice in the move.
Gale added the goal and increased his side’s lead to 8-0 with a penalty before Saints could draw breath but the visitors steadied the ship and hit back on 16 minutes through winger Regan Grace following nice work from classy full-back Ben Barba.
Castleford thought they had scored again when right winger Greg Minikin pounced on a handling error from Mark Percival but the try was disallowed for a knock-on and, aided by five successive penalties, St Helens finished the first half on top.
Substitute Louie McCarthy-Scarsbrook went close to touching down Matty Smith’s grubber kick before being held up over the line and the pressure told three minutes before the break when second rower Matty Knowles charged onto hooker James Roby’s smart pass from dummy half close the line.
Percival, who was wide with his first conversion attempt, was on target this time to put his side in front for the first time and they defended superbly in the early part of the second half to keep their lead intact.
They were helped in their efforts by Tigers stand-off Ben Roberts, who twice fumbled the ball in promising attacking positions and in between passed the ball into touch inside his own 20-metre area to put his side under pressure.
The home side were indebted to hooker Paul McShane for throwing Roby back from the line and they regained the lead on 57 minutes when Gale released winger Greg Eden inside his own half and was on hand to take a return pass.
Gale, who celebrated by lifting his shirt to display his bandaged stomach, converted his own try to make it 14-10 and was also on target after loose forward Adam Milner burrowed his way over for Castleford’s third try on 64 minutes.
Trailing 20-10, there seemed no way back for Saints but they turned the game on its head in a dramatic last 10 minutes.
First right winger Tommy Makinson went over in the right corner, Percival then crossed at the other corner and the outstanding Roby gratefully accepted an offload from Alex Walmsley to race clear and get centre Ryan Morgan over with less than three minutes left.
Percival was unable to add any of the conversions, however, and when Saints conceded a penalty for obstruction with 28 seconds to go Gale stepped up and landed the goal to level the scores and send the game into extra time.
Gale and Smith both failed with drop-goal attempts before the Castleford man finally hit the mark to send the bulk of the 11,235 crowd into raptures and bring to a sudden end one of the most dramatic matches in history.