Liverpool, who had twice held the lead, were broken at last. That goal from Henry was part of a hat-trick but the splendid endeavours of this great forward were lost within the importance of the simple result.
It followed removal from the FA Cup at the hands of Manchester United and eviction from the Champions League by Chelsea in the past week. Arsenal took a different sort of exhaustion from this afternoon. They could almost relish the weariness, enjoying it as a souvenir of an occasion that is likely to look crucial in the history of the club.
Arsenal remain unbeaten in the Premiership and the title still seems bound for Highbury despite the recent, barely stifled panic. The gnawing misery of the defeat by Chelsea should now fade. At most Arsène Wenger's team, who are seven points clear, require five wins from their remain- ing seven fixtures to be sure of fending off the Chelsea challenge.
Three of those are at home, against Leeds, Birmingham and Leicester. The sight of such names puts Arsenal's travails into context. It would always be possible for them to go down narrowly to a United or a Chelsea but they are much less at risk against the other members of the Premiership.
Yesterday's events emphasised the degree to which the top three clubs lead separate lives. Although Liverpool are vying with Newcastle for that fourth Champions League slot, they are not genuine members of the elite. It is still a shock to be presented with the sheer sparseness of the Anfield club.
There was miserable paucity in the sight of Igor Biscan, so often excoriated by overwrought Liverpool fans, attempting to deal with either Henry's forays or his cruel teasing of the offside trap. Elsewhere in Gérard Houllier's team talent dissolves until someone like Harry Kewell is a scarcely detectable presence.
There is some worth to the side but it depends on too few people and predictability is therefore unavoidable.
To the credit of the two meritorious performers, Steven Gerrard and Michel Owen did make their gifts tell despite a lack of assistance. After 42 minutes they combined for the goal that put Liverpool 2-1 ahead at the interval. Arsenal, lethargic and unprofessional then, stood off so that Gerrard could measure up the pass that Owen, making a lateral run behind Sol Campbell, fired in at the near post.
If defeat for Wenger's team appeared entirely possible at that stage, it was because of their own foibles much more than Liverpool's qualities. Tired as they are, it was confidence that was ebbing away from Arsenal.
One cannot imagine Wenger smashing his disappointing players against the dressing-room walls at half-time. Furious as he must have been with the insipid nature of the display, the manager performed wonders by drawing out the expressiveness and self-belief that had gone into hiding in these woebegone souls.
Wenger had certainly not sent them on to the field in the right frame of mind at the start. Arsenal almost made themselves vanish and there was nothing corporeal to the defending in the sixth minute when Gerrard had the first free header from Kewell's corner and Sami Hyypia the second to open the scoring.
The season would have had a wholly different character if Owen had doubled the advantage after half an hour but he dabbed John Arne Riise's long ball over the bar. Within a minute Henry had equalised. The striker often sets the side's mood and when he comes to life there is a bubbling personality to the other players as well.
In the build-up the committed Ashley Cole harried Dietmar Hamann and Robert Pires lobbed a pass into the left of the penalty area. Henry required one touch to control and the next to shoot. His drive went in off the far post, but he was already celebrating once he had struck it, so completely could he trust his instinct.
He had a part in the next equaliser as well, which brought the score level at 2-2 in the 49th minute, but it was Freddie Ljungberg who slid through a ball that Pires determinedly forced into the net. Then, within seconds, there came the breakthrough virtuosity of the afternoon.
Henry, taking possession in a deep position, went on an exhilarating run past Hamann and Biscan before putting a sleek finish past Jerzy Dudek. Dennis Bergkamp's chip sent him in again after 77 minutes and, although Dudek blocked the ball, it rebounded off Henry to reach the net.
Henry, in the aftermath of the Chelsea match, was not even expected to be fit for this occasion but, as with the injuries sustained by José Antonio Reyes and Ljungberg last weekend, the problem proved less serious than the original diagnosis. His condition for tomorrow's game at Newcastle must be questionable but the priority for Arsenal was to have him excel against Liverpool.
No one else could equal his high-speed grace but others did make a stand yesterday as well. Patrick Vieira proved to be the key, an unwavering influence in midfield, and the full-backs were also important. The tenacity and attacking of Cole are often noticed, yet Lauren's toughness and disinclination to allow Kewell scope were also vital to Arsenal.
All may not be exactly right with Wenger's team but, given the seven-point lead, they should be as good as they need to be in the next few weeks.