Put the green powder from the basket into Alexandra's tea.
Official in-game clue: "The cat also likes herbs. Maybe Rusty puked more than once."
Where: Day 1 Evening, during the tea service in the hallway.
Why it gets missed
The clue is about where the powder comes from, not where it goes. Reading the cat also likes herbs while holding a teacup does not obviously mean add this to Alexandra's drink, so the powder gets treated as scenery or as something for the cat.
The tea service is also a long chain with a scripted failure in the middle, which makes it easy to lose track of an optional step.
What to do
- Take the green powder from the basket.
- Build the tea in order: hot water → tea → milk → powder.
- Serve it to Alexandra.
The rest of the tea chain
Ask the maid for sugar, give the tea leaves to the cat first, take the cup from the room on the right. When you are told it is not sweet enough, add sugar — the cup cracks, and that is scripted. Repair it with the adhesive and add sugar a second time to advance.
Full sequence on the tea service page. The champagne in this same block belongs to the baby.
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.