EIGHT days after their stroll around Franklin's Gardens, Ulster made a mountain out of the Ravenhill return.
Now, instead of targeting a place as top seeds, they are looking over their shoulders in Pool 4 after losing the last 100pc record in European rugby.
Northampton were always going to respond to losing 25-6 on their own patch, and the question was whether the northern province could match their early intensity and get ahead.
They couldn't and, instead, Ulster conceded 10 points to the furiously committed English side in the opening 18 minutes and couldn't bridge the gap.
The low scoreline didn't reflect a gripping match between the last two beaten Heineken Cup finalists. Paddy Jackson's 43rd-minute penalty, which made the score 10-9, was the solitary score in the second half but that didn't take away from the drama.
Both sides had chances to score, with the television match official required to rule out efforts at either end.
The Saints caught a case of white-line fever every time they got within a sniff of a try during their dominance immediately after half-time, while Ruan Pienaar missed two difficult kicks to win it as Ulster's handling and scrummaging let them down on key occasions.
"Our execution tonight was poor and we suffered for it," Ulster head coach Mark Anscombe said.
"They got 10 points up in the first 18 minutes. We held them out well, a couple of times we were a bit lucky later on. But I think we created enough opportunities to score points and we weren't patient enough and didn't have any composure at crucial times. We tried to force it.
"They brought more passion than us at the start and their physicality got them going."
And so, the Saints became the first visiting team to win a European game at Ravenhill since Stade Francais in October 2008, inflicting Ulster's first loss in any competition since May's Heineken Cup final defeat and their first defeat at the venue since Treviso's shock win in October 2011.
"We've had so many great European nights at Ravenhill and that is why the players are hurting," captain Chris Henry said. "It wasn't what we were expecting, it is not what we are used to and it is not what big European nights in Ravenhill are about.
"We will learn from it and use the hurt. But, without a doubt, one defeat doesn't make us a bad team. We were never going to go through the season without losing a game, I think we were all realistic about that."
With a wounded Leinster visiting Belfast on Friday, before a trip to Thomond Park to take on Munster eight days later, there is a real test for Anscombe, who was tasting defeat for the first time as Ulster coach and whose resources are being stretched.
The loss of Tommy Bowe and an injury to Dan Tuohy will test his squad depth and it was clear on Saturday that Northampton, who had rotated their team more and looked fresher, had more bite on the bench, where just three of Ulster's replacements had ever started a Heineken Cup game.
Bowe's expected long-term absence with knee ligament damage is a major blow, and Tuohy's calf injury leaves them worryingly short at second-row in the short term. Iain Henderson put in a good defensive shift, but in comparison to the immense Man of the Match Samu Manoa and Courtney Lawes, he looked physically unready for second-row combat at this level.
Manoa led from the front with a robust display as the Saints took the game to Ulster from the kick-off, with Stephen Myler opening the scoring before South African GJ van Velze powered through Andrew Trimble's tackle and over the line in the corner.
Jackson kicked three of his four penalties either side of half-time to give Ulster a chance, but after surviving a Saints onslaught after the break, they then butchered chance after chance by dropping balls and conceding possession at the scrum.
A superb Paul Marshall break three minutes from time set up the dramatic conclusion. The replacement scrum-half spotted a gap and tore up the right, finding Bowe, who was hauled down outside the '22', damaging his knee in the process.
The Saints conceded a penalty after Tom Wood didn't release when held in the tackle, but Pienaar had to wait for almost 10 minutes as the medics tended to Bowe before the Springbok sent his effort wide.
"It makes it interesting now," Northampton coach Jim Mallinder said when assessing the pool. "Ulster still have to play Castres (away) and that's a difficult game for them. I think we can look forward to that. I think the two games have got something in it for us."
Despite the defeat, Anscombe knows that his side remain in control.
"There are three teams in it, with two games each and we're leading it by a few points (three)," the New Zealander reflected.
"We're still leading it with two games to go and our destiny is still in our hands. Not every team in this competition of 24 has that opportunity, we have just got to take it."
ULSTER – J Payne; T Bowe (N McComb 77), D Cave, P Wallace (L Marshall 68), A Trimble (C Gilroy 56); P Jackson (P Marshall 61), R Pienaar; T Court (C Black 68), R Best, J Afoa; I Henderson, D Tuohy (R Lutton 80); N Williams (R Diack 71), C Henry (capt), R Wilson.
NORTHAMPTON SAINTS – B Foden; K Pisi, G Pisi, T May, J Elliott; S Myler, L Dickson; S Tonga'uiha (A Waller 63), M Haywood (R McMillan 71), P Doran Jones (B Mujati 53); S Manoa, C Clark (M Sorenson 63); T Wood, P Dowson (capt), GJ van Velze (C Lawes 25).
REF – N Owens (Wales).