St Helens overcame stubborn part-time opponents to set up a derby clash with Warrington in the Coral Challenge Cup final on August 24.
Instead of cantering to their anticipated victory, the runaway Super League leaders were made to toil for a 26-2 success at the University of Bolton Stadium.
Leading only 8-2 at the break, the James Roby-inspired Saints ran in three tries without reply in the second half to secure their 22nd final but first for 11 years.
Remarkably, their showdown with Warrington, who were 22-14 winners over Hull in the other semi-final, will be the first time the pair have met in the final in the 122 years of the famous knockout competition.
The victory made up for the disappointment of defeat to Catalans Dragons in last year's semi-finals but most of the plaudits will go to Halifax, a mid-table Championship team who rose superbly to the occasion.
Halifax were the first club from outside the top flight to reach the last four since 2006 and, although they never seriously threatened to create history by making the final, they certainly pushed their illustrious opponents all the way.
Yes, the rain was a leveller but Halifax coach Simon Grix will be immensely proud of his courageous team of farmers and electricians who harried their full-time opponents to knock them off their stride.
St Helens coach Justin Holbrook brought back the nine players he rested for his side's 32-12 Super League defeat by London Broncos and they showed their opponents respect by kicking an early penalty, with Danny Richardson putting his side 2-0 in front after four minutes.
Attempting to put Saints off their game, Halifax tried the unorthodox with short kick-offs, and no one tried harder against the odds than skipper Scott Murrell who revelled in the occasion after missing out when Hull KR became the last non-Super League club to reach this stage.
Murrell forced a goal-line drop-out and, when he was taken out off the ball, centre Steve Tyrer, who began his career with St Helens, kicked Halifax level.
A combination of wet ball and committed one-on-one defence from the underdogs continued to thwart Holbrook's highly-fancied men.
Louie McCarthy-Scarsbrook and Alex Walmsley both lost their grip on the slippery ball as they strove for the line, and even the normally immaculate Tommy Makinson fumbled following a trademark acrobatic dive at the corner.
The breakthrough eventually came five minutes before half-time when Roby forced his way past a clutch of defenders for the game's opening try, with Richardson's conversion making it 8-2.
That was expected to open the floodgates but it turned out to be little more than a trickle as Halifax battled to the end.
Second rower Dominique Peyroux grabbed another short-range try seven minutes into the second half and, as the part-timers understandably began to tire, the gaps began to open up.
Roby combined with Richardson to get full-back Jonny Lomax over, and he later put in a neat grubber kick for stand-off Theo Fages to touch down.
Richardson maintained his 100 per cent record with his fifth goal to wrap up the scoring.
