You could say it was the stuff of nightmares - but what happened at Franklin’s Gardens on Saturday evening may even have been beyond Saints supporters’ wildest hallucinations.
Six tries conceded, one scored. Leinster played rugby from a different planet to bring Northampton, who had won their previous seven games, crashing down to earth.
It was a savage reality check for Jim Mallinder’s men.
They hadn’t played to their full potential in recent wins against Newcastle and Worcester, but still prevailed.
This, though, was a different challenge altogether. A below-par performance against Leinster will be punished. And so it was. In crushing fashion.
Saints got a taste of their own medicine.
They had done to them what they have inflicted on plenty of others this season.
Leinster, as acknowledged by all fair-minded fans at the Gardens, were far too good. They were unrelenting and ruthless.
Saints were caught cold and couldn’t get into the stride that has served them so well this season.
It was reminiscent of last December, when Ulster came to town and did a 25-6 demolition job.
This was worse than that, though. An evisceration of the sort Leicester dished out at the Gardens in March.
The common denominator? Matt O’Connor, the Leinster boss and former Tigers coach.
His smile in the press room after the game said it all. Two visits to Northampton in 2013. A 76-15 personal aggregate win.
As for the Saints representatives put in the firing line after the game; Tom Wood and Jim Mallinder were refreshing.
There was no hiding place - and they didn’t seek one.
They gave a brutally honest assessment of what they had just witnessed, struggling to find positives.
One is that Saints have been here before.
That Ulster defeat last December was followed by a defiant display in Belfast, resulting in a brilliant 10-9 win.
Whether Saints can do that this time remains to be seen.
They are are currently blighted by injuries to key men, a story told by the sight of Alex Corbisiero and Ben Foden suited and booted on the pitch at half-time.
Corbisiero, who is out for between three to four months with a knee injury, was on crutches, Foden, out for a similar spell, in a surgical boot.
The first-half performance was that bad, you almost wanted to put them on at the break to see what they could do.
How Saints could have done with them fully fit and at their best. Big-name players are required when the big games come around.
Kahn Fotuali’i, James Wilson and George Pisi were also unavailable. How they were missed.
A last-minute reshuffle, sparked by Wilson’s post-warm-up withdrawal, pushed Ken Pisi to full-back, which is not a position he is used to. It didn’t work, and Leinster took advantage.
Pisi had highlighted Brian O’Driscoll as his childhood hero in the build-up to the game, and the Ireland legend showed why he is so revered with a sensational all-round display.
Pisi’s dreams of facing his idol were to turn into harsh reality.
For Saints there was a similar grounding effect.
The win they had fantasised about got further away with every passing second.
Now they will have to dream big if they are to believe they can repeat last year’s Ravenhill rally at the Aviva Stadium next Saturday.
How they rated...
Was thrown in at the deep end in a full-back position he is not used to and was given a torrid time. Leinster peppered him and despite showing plenty of desire, he found it tough... 5
Came in at the last minute for the injured James Wilson and had little chance to make an impression as Saints failed to put any phases together... 5
Tried to give Saints some go-forward, but was not the only one who struggled to do that. A tough night in the midfield... 5
A beacon of light amid the gloom, the big centre was positive whenever he got the ball and tried to push Leinster back... 6
The Wales wing hadn’t played for his club since October 20 and this was not the return he had dreamed of. Didn’t have possession in good positions... 5
Couldn’t control the game as he has on so many other occasions this season. A quiet night from the tee as Saints were always playing catch-up... 5
Scored Saints’ only try of the game and continually tried to cajole his team-mates, but there was little he could do... 5
The Leinster pack gave Saints a tough night, but the scrum wasn’t the worst part of their game and this man will have learned a lot from the defeat... 5
The skipper had an unusually off night in the lineout, with Christian Day not there to dictate proceedings in the first half, and saw opposite number Sean Cronin have a huge game... 5
Came in at the last minute and was soon shedding claret for the cause, but couldn’t help Saints dominate up front... 5
Like Burrell, showed determination to shrug off the disappointment of Leinster’s early scores, but his battling was in vain... 6
Started with a couple of great tackles, but couldn’t impose himself on the game as he would have wanted and things didn’t go smoothly in the lineout... 5
Gritted his teeth and dug in as things continued to get worse, but couldn’t drag his team back into the game... 6
Came on and made a big difference at Worcester a week earlier, but this was a different level and even the inspirational flanker could do nothing to stop the blue tide... 5
Tried hard to get Saints out of their own half early on, but this was a difficult day at the office for the No.8... 5
Replacements (who played more than 80 minutes)
CHRISTIAN DAY (for Dickinson 40)
The influential lock was left out of the starting 15 in favour of the raw power of Samu Manoa and Courtney Lawes, but he was eventually needed as the ship was far from steady... 5
MIKE HAYWOOD (for Hartley 58)
A tough ask for the young hooker to come on in such circumstances, but he didn’t do too much wrong... 5
ETHAN WALLER (for A Waller 58)
Came on for his brother as Saints looked to at least get on top in the scrum and not much he could have done about the end result... 5
CALUM CLARK (for Dowson 58)
Thrives on adding energy to proceedings, but Saints’ race was already run by the time this breakdown expert entered the field... 5