The mesmerising finish with a 16-pass move that criss-crossed the pitch, and had Harry Robertson beat a number of tackles along the way, sets up a semi-final trip to Hull KR on Saturday, 4 October.
As Super League’s two most successful clubs, sharing 17 Grand Final wins between them, the showdown at Headingley between the fourth and fifth placed teams promised to enthral.
Both sides made a number of changes for the knockout tie, with Saints’ backs reshuffled after winger Kyle Feldt was injured in last week’s win against Castleford, while Leeds could again call on the prolific Ryan Hall and Man of Steel nominee Jake Connor.
Scrum-half Connor played a part in Leeds’ opening try, with the ball quickly shifted through the hands of Lachie Miller and Ash Handley before finding Hankinson to dive over.
The try from Hankinson, after he spilled a high ball at the other end to invite pressure on Leeds, summed up the chaotic nature of the opening exchanges.
A combination of luck and quick thinking had Saints pull level, after Curtis Sironen managed to take a high kick before then offloading for Morgan Knowles, who spilled the ball.
The forward, however, thrust a boot out to turn what seemed destined to be a knock-on into a sublime grubber kick for Lomax to finish.
McDonnell went on to restore Leeds’ advantage as he bobbed and weaved his way through three attempted tackles to touch down on the half-hour mark.
Lees’ departure at half-time left Saints short on the bench on a physically taxing night in West Yorkshire as Leeds piled forward in search of more tries after the break.
Leeds went on to waste a succession of chances to add to their lead, with a captain’s challenge from Saints also seeing a Handley try scrubbed off.
At the other end it took a try-saving shove from Connor to keep Bennison from crossing over on the hour mark.
But the winger would go on to pull a try back to give Saints hope with four minutes left after Connor had put the hosts eight points up with his penalty.
A Leeds penalty conceded for offside allowed Saints one last chance to salvage a memorable result, which Wright did for the club that gave his season renewed purpose after leaving financially-troubled side Salford on loan in August.