Saints looked certain to register their worst run for 34 years after an abject first quarter in which their confidence appeared to be at rock bottom. But their fortunes were transformed in remarkable fashion.
They pulled two tries back in six minutes before half-time and ran in three more in a 10-minute spell early in the second half, two of them by winger Tom Makinson (pictured), who finished with 14 points. Then, after Leeds threatened a late fightback, 18-year-old prop Luke Thompson, playing only his third Super League match, went over for the match-clinching try that lifts Saints back into the top eight and breathes new life into their season.
The Rhinos, who gave a debut to 18-year-old Liam Sutcliffe, punished handling errors inside their own 20-metre area by Jordan Turner and Thompson to create the position for Kallum Watkins, restored to his customary centre spot, to take Zak Hardaker's pass and open the scoring with his ninth try in the last seven games.
Four minutes later dangerous centre Joel Moon took Danny McGuire's pass and jinked past Nathan Ashe before stretching out of Jon Wilkin's tackle to touch down.
Saints had second rower Sia Soliola put on report for what looked to be a shoulder charge on McGuire in the build-up to the try and things got worse for the visitors midway through the first half when Rob Burrow dummied his way over for a soft try. Kevin Sinfield kicked a second goal to make it 16-0 but Saints struck back with two quickfire tries to claw their way back into the contest.
Both scores were the result of smart work at dummy half by Stuart Howarth, whose neatly timed passes opened up the Leeds defence to create gaps for Louie McCarthy-Scarsbrook and Soliola to stroll through. Makinson added both conversions to cut the gap to just four points and he brought the scores level three minutes into the second half with the try of the match.
Willie Manu started off a 70-metre move with a tremendous pass out of the tackle to release Mark Percival and he went on to draw Hardaker before releasing his winger. Makinson was wide with the goalkick but Saints were in front for the first time four minutes later when Hardaker tried to get the ball back in play to avoid a goal-line drop-out but succeeded only in gifting a try to Saints prop Anthony Laffranchi.
Makinson kicked his third goal and Saints stretched their lead to 26-16 five minutes later when Paul Wellens' grubber kick on the last tackle eluded the unfortunate Hardaker and Makinson pounced for his second try.
The game threatened to take another twist when a charging run by Leeds second rower Jamie Jones-Buchanan set up the position for prop Ryan Bailey to take Burrow's pass from just short of the line to crash over for his side's fourth's try on 58 minutes. But there was no way back for the champions when Thompson scored his second try for the club.