Everywhere you looked, people were losing their heads.
There was Ángel Di María stamping on Fernandinho. There was Leandro Paredes hurling the ball at an opponent. There was Marco Verratti, seconds after being booked, pulling Riyad Mahrez's shirt. There was Presnel Kimpembe and Danilo flying into challenges.
There was Mauricio Pochettino, having at one point marched on to the pitch to try to calm his side, giving up and sitting glowering on the bench.
And there was the Dutch referee Björn Kuipers smiling beatifically, determinedly keeping 21 players on the pitch, although had one of those late lunges brought a serious injury, his failure to produce more than one red card would have seemed questionable.
And against that, as bottle went and dignity with it, were Manchester City, implacable and magisterial. Perhaps it is easy to look mature when the immediate comparison is a team of Veruca Salts but, still, this was a side that have suffered blowout after blowout in Europe, led by a coach who has come to be as defined by his struggles with the caprices of the Champions League as by his successes elsewhere.
They could have wobbled, as they have so often in the past, but they did not. There have been more obviously brilliant performances by City, but none surely so composed or so complete.
When Mahrez scored his second, there was, including injury time, half an hour or so to be played: plenty of time for one goal that might have planted a seed of doubt and led to three, particularly against a team that have been disappointed so often.
Paris Saint-Germain didn't even try, but fell to petulance and self-pity that they subsequently tried to justify by claiming Kuipers had sworn at them: that's the sense of entitlement perpetual success will bring. It's also the one caveat in hailing City's newfound tranquillity: PSG fell apart long before City had a chance to.
But City this season have been generally calmer. There has been a shift in midfield that, after a difficult start, has made them look more secure. It’s tempting to discern the influence of Pep Guardiola’s mentor Juanma Lillo, who was named as his assistant, but whatever the cause, City’s press is less frenetic this season, better targeted.
The striking aspect of Tuesday’s game was the almost orthodox nature of much of their defensive play in the first half, getting men behind the ball, squeezing the space into which PSG wanted to run.
Their task was made easier, of course, by the absence of Kylian Mbappé with a calf injury, but that is the problem when you blow the budget on two megastars: occasionally one will be injured for a key game, and then the other one can be smothered relatively easily while the deficiencies elsewhere are exposed.
Marquinhos plus some others may be a viable defensive strategy in Ligue 1 (although perhaps not, given PSG’s problems there this season) but it certainly isn’t in the latter stages of the Champions League.
Whatever concerns there may be about the level of City’s spending, or the source of that wealth, it has been well directed. Almost unthinkably for a super-club, if there is a shortcoming in the squad, it is at centre-forward.
The signing of Rúben Dias last summer has been as transformative as that of Virgil van Dijk was for Liverpool. It's not just that he is an excellent defender – and he made at least three exceptional blocks against PSG – it's that he makes those around him better players.
The Portugal centre-back was probably the standout player for City, but this was a night on which everybody played their part. Oleksandr Zinchenko may have been a slightly surprising selection ahead of João Cancelo, but he excelled, both with his discipline and his forward surges, one of which brought the opening goal.
The inclusion of Fernandinho rather than Rodri perhaps also raised an eyebrow but on his 36th birthday he was a commanding, authoritative figure at the base of midfield. His reaction after Zinchenko had been (harshly) booked for reacting to Paredes throwing the ball at Phil Foden was telling: he was not going to allow PSG's indiscipline to infect his side.
And of course he was in part the provocateur, for nobody in the modern game is so good at evading yellow cards for what appear to be bookable fouls. Quite how he acquired Mark van Bommel’s cloak of invisibility nobody knows, but it is a useful weapon to have.
The latter stages of the Champions League in recent years have tended to the thrilling and the frenzied, teams who are not used to defending, not psychologically equipped to endure pressure, flailing at each other and frequently collapsing. It’s all been very entertaining, but the sense has been that if any super-club could work out how to fuse a modern pressing game with a defence worthy of the name, it would have a significant advantage.
City, perhaps, have now done that. It probably helps them to play in the Premier League which, for all its faults, remains far more generally and consistently competitive (some odd results in France, Spain and Italy in this notably weird season do not suddenly transform the nature of their leagues) than any of Europe's other major competitions. They are tested on a more regular basis.
But fundamentally Tuesday was a victory for a philosophy, the triumph of the collective over the individual.