|Racing Metro (10) 20|
|Tries: Van der Merwe, Andreu Cons: Sexton, Goosen Pens: Sexton 2|
|Northampton (3) 11|
|Try: Dowson Pens: Myler 2|
Northampton shot themselves in the foot as Racing Metro's Johannes Goosen converted Marc Andreu's last-gasp try to deny Saints a losing bonus point in the European Rugby Champions Cup.
Trailing by two points Saints tried to run from deep but Ben Foden's chip was charged down by the 5ft 5in Andreu.
The hosts had been helped into a 10-3 lead at the break by Francois Van Der Merwe's early converted score.
Phil Dowson's try had got Saints within two points before they self-destructed.
It was a scrappy game with constant scrum penalties interrupting the flow, and having lost two men to the sin bin the hosts will be delighted that Northampton left with nothing.
Racing started quickly in Paris and went ahead through South African second row Van der Merwe's converted score as their forward power told.
Northampton have been in fine form and lead the English Premiership by three points, but the home pack had the edge and it took the visitors half an hour to get on the board, courtesy of a Stephen Myler penalty.
When the game did get going in the first half Racing looked the more threatening, with Ireland fly-half Johnny Sexton lively with ball in hand, and when yet another scrum ended in a shrill whistle, he gave the hosts a 10-3 half-time lead.
Northampton looked better after the break and Myler trimmed the gap with his second penalty as the game swung in their favour.
Sexton missed a simple penalty and the hosts' luck went from bad to worse as they had prop Julien Brugnaut sin-binned after another messy scrum - fellow prop Eddy Ben Arous was binned for going offside at a ruck later in the game for the hosts.
Northampton looked set to take the lead when George Pisi intercepted and seemed certain to score under the posts.
But the Samoa centre appeared to pull a hamstring and spilled the ball 10 metres from the line before hitting the deck and having to be helped from the pitch.
A second Sexton penalty restored Racing's seven-point lead but Northampton gave themselves the chance of a draw as replacement back-rower Dowson finished off a fine passing move that started near halfway.
Myler could have levelled the scores but the fly-half was well wide with a tricky kick and Saints kissed goodbye to even a losing bonus point when they tried to attack from deep and the diminutive Andreu pounced.
Northampton director of rugby Jim Mallinder: "It's really disappointing because we were within seven points all game, so losing the bonus point at the last minute is a blow.
"But I can't criticise the efforts of my players or their ambitions in trying to win the game.
"Racing are a very good team as we know, they are very physical, strong and probably different from most of the teams we will face in the Premiership.
"But there are still five more games so we are not too down."
Racing fly-half Jonny Sexton: "To go from it looking like it being a draw and getting four points to zero is very important.
"The big difference between Top 14 and Champions Cup is that every point and try counts.
"The most important thing for the French mind-set is that we have something to play for, if we hadn't had won then I don't think we would have bothered much with the tournament but now we have got a win."
Racing Metro 92: Dulin; Imhoff, Dumoulin, Roberts, Andreu; Sexton, Machenaud; Brugnaut, Lacombe, Ducalcon, Kruger, Van Der Merwe, Lauret, Le Roux, Claassen.
Replacements: Audrin for Dumoulin (79), Phillips for Machenaud (62), Maurouard for Lacombe (62), Mujati for Ducalcon (63), Charteris for Van Der Merwe (44), Ben Arous for Lauret (58), Goosen for Sexton (73).
Not Used: Gerondeau
Sin Bin: Brugnaut (55), Ben Arous (74).
Northampton: Foden; K Pisi, G Pisi, Burrell, North; Myler, Fotuali'i, A Waller, Hartley, Ma'afu, Lawes, C Day, Wood, Clark, Manoa.
Replacements: Elliott for G Pisi (57), Dickson for Fotuali'i (57), E Waller for A Waller (67), Haywood for Hartley (64), Denman for Ma'afu (61), Dowson for Lawes (71), Craig for C Day (72).
Not Used: Wilson.
Ref: George Clancy (Ireland).