A team that has proved Jekyll and Hyde in European competition in recent years had supporters at home hiding behind their sofas and those at the ground covering their eyes.
The deficit was an alarming 27 points by half-time, coughing up memories of that night at Franklin’s Gardens in December, 2013, when Leinster ran riot in the first 40 minutes.
And as on that night, the strains of the opposition crowd weighed heavy on Saints souls, with the ear-splitting sound produced by Les Jaunards supporters inducing a headache.
Saints had been desperate to silence the crowd.
To score early, just as they had done in sensational successes at Ulster and Leinster in seasons gone by.
But once Clermont went 10-0 up and Stephen Myler missed a penalty to put Saints on the board, the warning signs were loud and clear.
The home fans, whose bouncing shook the stands, and the physicality of the home players had rattled a Northampton team so used to being the ones doing the rattling.
The Saints pack has built a fearsome reputation in Europe under forwards coach Dorian West since the class of 2011 crushed all before them.
But on this occasion, Clermont played the role of playground bullies, pushing their English opponents around with excruciating ease.
The ever-frank Tom Wood compared it to an open training session with a tweet that did the rounds after the game.
And, to their credit, there was certainly no shying away from Saints players or staff.
They did not make any excuses for a performance that, as has been said a few times in recent months, was the antithesis of ones Saints have become revered for producing.
On the flip side of the coin, Clermont’s rapier-like attack and teak-tough defence was praiseworthy.
The Top 14 team enjoy a huge budget, and have used it well, assembling a group of galacticos who will take some stopping in this season’s competition.
They will host Saracens next and though you would expect the boys from Barnet to be on their guard after what happened to Saints, you can’t see past a Clermont win.
In the post-match press conference, Mallinder was asked whether he felt the French team could win the Champions Cup.
And his wry smile and firm “yes” said all you needed to know about how good the men from the Auvergne region had been during the previous 80 minutes.
For Saints, it is now a case of rebuilding.
Of enduring what used to be known as a video nasty during the week and coming back stronger at Exeter next Sunday.
It is not like they have not done it before, with the aforementioned Jekyll and Hyde nature having shown itself on numerous occasions in the past.
And there is still plenty to play for, with the chance of retaining the Aviva Premiership crown they claimed last season very much on the cards.
But it is clear that Europe’s best are just a bit too good right now, in which there is no shame.
When you consider Clermont’s third choice kicker, Mike Delany, reportedly gets paid what one of Saints’ key men earns, you can see why there is such a gulf.
But Mallinder and his men rightly expected to do so much better.
They are the champions of England for a reason, but they simply didn’t show it on this occasion.
And now they will need all they have got to ensure one failure to make a Twickenham final doesn’t end lead to another.
How they rated...
Made one superb tap tackle to stop Wesley Fofana in his tracks, but his attacking was less influential than his defending... 5
Had a nightmare task on his hands to try to stop Noa Nakaitaci, who grabbed two tries as Clermont swarmed all over Saints... 5
Lost the ball in contact as Nick Abendanon sprinted clear to score Clermont’s fourth try, but did try to put himself about a bit... 5
Tried to use his power to get Saints up the pitch, but he was met with a white wall of resistance at every turn... 5
Came into the side in place of George North and couldn’t have an impact on the game on a tough night for the team... 5
Was unusually wayward with the boot, missing both of his shots at goal and he was unable to exert any control on the game as the forwards lost the battle... 4
Had a torrid time in the first half, with his box-kicking causing Saints problems rathers than getting them out of trouble... 4
Tried to stand his ground in the scrum, but Clermont were getting the calls and their power was too much... 5
Tried to keep his team focused, but they had an unenviable task after Clermont flew into an early lead... 5
Had a really tough night in the scrum, coming close to earning a yellow card as Vincent Debaty turned the screw... 4
Usually a man to grab the game by the scruff of the neck, the American was unable to exert any real influence... 5
Was forced off at half-time with a shoulder injury and was not able to have the kind of impact he usually has on the game... 5
Frantically tried to get a grip on proceedings, but Clermont were simply too strong and too quick in all areas... 5
Gave it everything as usual but Clermont sussed Saints out at the breakdown and stopped him having his usual say... 5
A powerful player, the big No.8 was nullified by some strong home defending as he tried to get over the gainline... 5
Replacements (who played more than 20 minutes)
CHRISTIAN DAY (for Lawes 40)
Saints never look the same team when this man doesn’t start - as he didn’t when they were thrashed by Leinster in 2013 - and his introduction helped steady things slightly... 6
KAHN FOTUALI’I (for Dickson 52)
Was perhaps a surprise omission from the starting 15 and did try to bring things to life when he came on... 6
ALEX WALLER (for Corbisiero 55)
Grabbed Saints’ consolation try and showed he was fired up after getting involved in some fisticuffs that went unpunished... 6
GARETH DENMAN (for Ma’afu 55)
Tightened things up at the set piece slightly and will be hoping to get some starts in the coming weeks... 6
JON FISHER (for Dickinson 55)
Added a bit more brute strength as he tried to help Saints salvage some pride on a really difficult night... 6
AHSEE TUALA (for Wilson 59)
Not an easy situation for him to come into, but he at least had less pressure and was keen to show his worth... 6
CHRON STAR MAN - Nick Abendanon (Clermont Auvergne)