不知何故 Nobody Knows How It Happened
眾卿道：「主公啊，不知何故，臣等一夜把頭髮都沒了。」國王執了這沒頭髮之表，下龍床對群臣道：「果然不知何故，朕宮中大小人等，一夜也盡沒了頭髮。」众卿道：「主公啊，不知何故，臣等一夜把头发都没了。」国王执了这没头发之表，下龙床对群臣道：「果然不知何故，朕宫中大小人等，一夜也尽没了头发。」
逐句解 Line by line
The ministers said, "Your Majesty, we cannot tell how it came about, but in a single night the hair of every one of us is gone."
They finally say it. 不知何故 — no idea why — is the phrase they will pass back and forth for the rest of the scene, and it is doing real work: an official who cannot explain a thing to his sovereign is in danger, so the ignorance has to be stated up front.
The king took up this memorial on the loss of hair, came down from the dragon couch, and said to the assembled ministers, "Indeed I cannot tell how it came about. Every soul in my palace, high and low, lost their hair in a single night as well."
He comes down off the throne to say it, which is the tell — this is no longer a matter he can rule on from above. 朕 is the imperial first person, reserved to the emperor since the Qin. 盡 is jìn, entirely, and note the phrase the narrator hands him: 沒頭髮之表, a memorial on the subject of no hair, filed like any other item of government paperwork.
The scene works by mirroring. The ministers report their bald heads; the king reports his bald palace. Neither can account for it, and the symmetry quietly tells the reader the reach of what Pilgrim did overnight — not a prank on the court but a clean sweep of the whole capital.
There is a bureaucratic joke buried in the wording. A Ming memorial was a formal instrument with a subject heading, and the novel gives this one its heading in full: the no-hair memorial. Whatever else has happened, the paperwork was correct.