By November 1630, Cardinal Richelieu had been chief minister for six years, and had made enemies of nearly everyone at court. His policy — alliance with Protestant powers against Habsburg Spain, in preference to a Catholic front — was opposed by the devout party, by the queen, by the king's brother, and above all by Marie de Médici, the king's mother, who had sponsored Richelieu's rise and now wanted him destroyed.
At the Luxembourg Palace on 10 November she confronted Louis XIII, in a scene that concluded with her demanding a choice between herself and the cardinal. Richelieu, who had entered through a side door, was present for part of it. She won. The king left without contradicting her.
The court concluded that Richelieu was finished. Courtiers went to the Luxembourg to congratulate Marie and to secure position under the new arrangement. Offices were discussed. People declared themselves.
Richelieu prepared to leave for Le Havre.
The king had gone to Versailles — then a small hunting lodge — and that evening summoned Richelieu, told him to remain in office, and confirmed his support. The following day the exiles were named. Marie de Médici was eventually confined and then fled the country, dying in exile. Michel de Marillac, Keeper of the Seals, was arrested; his brother, a marshal of France, was tried and executed.
The day acquired its name from the people who had spent an afternoon congratulating the wrong party.
Two mechanisms are worth extracting, and they are both about timing rather than about intrigue.
The first is letting a plot mature. Richelieu had known about the opposition for months and had not moved against it. An adversary who is suppressed early disperses and reassembles; an adversary who is allowed to believe he has won will declare himself publicly, name his allies, and forfeit deniability. The commitment principle of chapter 3 works against its holders here — a courtier who has spent an afternoon congratulating the victor cannot afterwards claim neutrality.
The second is the false consensus of chapter 28. Marie's faction was a closed social bubble in which everyone agreed and everyone's agreement was evidence to everyone else. What they never checked was the only opinion that mattered, and they could not have checked it, because the king had not spoken.
Richelieu's lasting institutional legacy was an intelligence service under Père Joseph, whose function was precisely this: knowing who believed what, before anyone else did, and therefore controlling when the reveal happened.
Aftermath & Cross-Reference: Intelligence Asymmetry as Weapon