When Stephen Myler lined up a drop goal in the dying seconds at the Madejski Stadium, you could almost see the pendulum swinging.
But which way would it go?
Would it go the way of Saints, who in recent years have been so adept at winning games with the final kick?
Or would it go the way of plucky underdogs London Irish, continuing the theme of Northampton’s season so far?
As it was, Myler saw his kick charged down, Irish eventually got the ball back and Saints slumped on the turf as the home side booted the ball out to secure a memorable win.
“Merry Christmas,” declared the London Irish PA announcer, whose impression of Pirates of the Caribbean character Jack Sparrow was uncanny.
But rather than filling their faces watching the film on television on Boxing Day, Saints had to listen to the irksome pirate rub salt in the wounds as their team suffered another defeat.
It was tough to take as, with 18 minutes to go, it looked like Jim Mallinder’s men would do what they became so good at last season: snatching a victory they may not have merited.
Kahn Fotuali’i’s try had given them the lead for the first time in the game, and Irish looked tired.
And when the home side lost Aseli Tikoirotuma to the bin three minutes later, it really did look all over.
Surely, the team who had failed to win any of their first six Aviva Premiership games were now beaten?
Surely, Saints would grind them into the ground during the yellow card period, which took up 10 of the final 15 minutes?
But no, Irish stubbornly held out and showed belief that many sides in their position wouldn’t have done.
They went back up the other end and forced Jamie Gibson to infringe, with the former Irish flanker sent to the bin.
And from then on, Irish always looked likely to win it, forcing a penalty try at a scrum and seeing Shane Geraghty stick the knife into his old club with a match-winning conversion.
It was a microcosm of Saints’ season so far.
Because, aside from the win at Bath earlier this month, Northampton have not shown the same steel that saw them top the regular-season table last time round.
They have displayed an inability to close games out, or to nick a late match-winning try or penalty in a frantic finale.
At Worcester on the opening night, they played poorly and predictably and were beaten by Tom Heathcote’s last-gasp drop goal.
At Sale, they again failed to show any real star quality and were unable to get anything late on, despite a period of pressure.
It looked like the tide had turned at The Rec, when JJ Hanrahan secured a late win with a composed penalty attempt.
But Irish stepped up when it mattered and ensured that the Bath win still looks like an anomalie rather than the start of a trend.
So what has gone wrong?
Where has that Saints swagger gone?
They used to roll into rugby grounds up and down the country and believe that the outcome was inevitable.
During their title-winning season, they never knew when they were beaten, snatching a succession of victories from the jaws of defeat.
Myler, nicknamed the Iceman by his team-mates, became hated by opposition sides as he routinely landed late penalties to secure the points.
But that belief seems to have deserted Saints so far this season.
Teams no longer feel that is inevitable Mallinder’s men will rob them late on.
Instead, belief is growing among other Premiership teams that they can match Saints.
Irish did that, stopping their threats up front and even edging them in some areas.
Saints gave them a shot in the arm with a sluggish start, continually kicking poorly to give the home side possession.
And by the time Mallinder’s men got started, they were already 15-3 down.
Then, Ken Pisi scored a try that looked so simple you wondered why it had taken Saints 36 minutes to muster it.
The reason for that was their poor kicking from their own half, Fotuali’i’s stunning box-kick into the Irish 22 aside, and their inability to move the ball quickly when they had it.
Instead, they again turned to the forwards to put the squeeze on, trying to use power to push Irish over.
But it didn’t work and the backs were left frustrated, with numbers continually in their favour as Irish threw the majority of their men in to defend the forward surges.
The home side’s tactics worked, until Pisi broke their resistance at the end of a rare backs move.
And Saints finally realised that was the way forward in the second period as Fotuali’i started to cut Irish apart and Tom Collins added some X factor from the bench.
It just showed that when Saints do trust their backs in attacking areas - as they did in a stunning win at Glasgow last month - they can do the business.
And on a mild day, they should have done it far earlier, while the backs should also have shown more self-confidence when they got the ball in their own half.
As it was, Irish’s spirit eventually told and they secured an unlikely win.
It ends the year on a high for them, but for Saints it is a final blow in a 12-month period that has not been kind to them.
They have won just 14 of their 29 matches during 2015, with a win percentage of just over 48 per cent.
Compare that with 2014, when Saints won 28 of their 36 games, with a win percentage of almost 78 per cent, and it makes for painful reading for the club’s fans.
It also makes a seventh successive top-four finish look unlikely, with trips to Leicester, Saracens, Exeter, Wasps and Harlequins, among others, still on the 2015/16 agenda.
But one thing every fan who has been following Saints during the past few years will know is that this is a club that specialises in surprises.
They are just as capable of losing at London Irish as they are of winning at Saracens.
And that gives hope for the first day of 2016, when in-form Exeter Chiefs come calling at Franklin’s Gardens.
What Saints also need now is a bit more luck on the injury front.
Because whether you are Northampton or Newcastle, Leicester or London Irish, you will usually fail to fire on all cylinders if you are missing a host of key men.
Saints can’t make excuses - and the fantastic form of Teimana Harrison shows the quality they have in reserve - but they are without the likes of Calum Clark and Tom Wood.
Clark, Alex Corbisiero and talented Kiwi utility back James Wilson have all yet to play a first-team game this season.
And there is no doubt that each of those men, when at full fitness and in form, would add an abundance of quality to this team.
However, Saints must continue to cope, and the knee injury to Kieran Brookes, which will keep November’s player of the month out for ‘quite a while’, is another thing to navigate.
They will hope Brookes, Clark and Corbisiero make speedy recoveries in the new year to maximise the squad in what is an incomparably brutal campaign.
If ever there was a season when you couldn’t afford big injuries, this is it, with no LV= Cup games to break up the intensity and give chances to reintegrate players.
But Saints will have to start to come to terms with that from the first day of 2016 onwards.
And if they can do that, the pendulum may yet swing back their way this season.
How they rated...
Was hit by a piledriver tackle by Aseli Tikoirotuma, which earned the Irish winger a yellow card, and overall it wasn’t a pleasant afternoon for the Saints full-back... 5
Got his name on the scoresheet towards the end of the first half, but his lack of recent match action showed as he made some uncharacteristic mistakes... 5
Put himself about as usual as he tried to stand up to Irish’s midfield and he also got a couple of nice passes away to keep attacks ticking over.. 6
Was replaced during the second half on a day that wasn’t what we’re used to seeing from the powerhouse centre... 5
Finally got his name on the scoresheet as he notched his first try of the season. Tried to get in the game and made a couple of decent breaks, but Irish shackled him well... 6
Not a good day for the fly-half, whose kicking from hand and tee was unusually poor and he will want to forget this game quickly... 4
KAHN FOTUALI’I - CHRON STAR MAN
In contrast to his half-back partner, the Samoan was able to pull the strings as he scored one and superbly set up another. A great display amid the gloom of defeat... 8
Eventually came off to be replaced by his brother, but had not put in a bad shift up until then... 6
Was making his first appearance since November 7 and despite that recent lack of action, he did well, keeping the set piece secure while he was on the field and working hard... 6
Still learning his trade and Irish did well against Saints up front, but the youngster didn’t do too much wrong... 6
Tried to help Saints front up, but wasn’t sharp enough on a couple of occasions as Irish built belief... 5
The assured presence of the experienced lock couldn’t help Saints early on, but he did his best to help them grow into the game... 5
Put himself about and desperately tried to bulldoze through the Irish rearguard, but the home side dealt with him well... 6
Was sent to the sin bin late on against his old team and this was a far from happy return as Irish scored the winner while he was off the field... 4
Along with Fotuali’i, this man was one of Saints’ real positives as he gained so much ground with some huge carries and also defended well. So impressive at the moment... 7
Replacements (who played more than 20 minutes)
ALEX WALLER (for E Waller 58)
Came on at a time when Saints were on top and helped them stay there until Irish’s late fightback... 6
SAM DICKINSON (for Paterson 58)
Has enjoyed a good season so far, but the big No.8’s power was nullified by Irish on this occasion... 6
JJ HANRAHAN (for Burrell 58)
Saints fans always love seeing the creative Irishman introduced and he did his best to add some spark... 6