Give the champagne bottle to baby James — before William.
Official in-game clue: "Someone else wants a drink. Why is this baby so fussy?"
Where: Day 1 Evening, during the reunion, in the same block as the tea service.
Why it gets missed
The champagne is handed to you in a scene where William is the obvious recipient: he is an adult, he is holding court, and the game does not suggest an infant should be drinking. Give it to him and the scene advances normally with nothing lost except this achievement.
The clue is doing the work here — someone else wants a drink is the whole hint, and why is this baby so fussy tells you which someone.
What to do
- Take the champagne bottle when it becomes available.
- Use it on James, the baby, not on William.
- Carry on with the evening as normal.
This does not block anything. William gets his drink afterwards and the reunion proceeds.
The pattern this belongs to
A large share of this game's hidden achievements fire when you do a chore wrong on purpose — failing the morning exercises, letting the goat eat the bouquet, scrubbing the portrait instead of the floor. Once you notice the pattern, the rest of the day gets easier to read.
Nearby
The full list of hidden achievements, in the order you reach them, is on the triggers page. Going for everything in one run? See 100% completion.