Ninth Case Achievement in The Case of the Golden Idol

You technically only need to find the clues required for the solution. Every clue in the game is marked with a ?/! and will turn into a check mark when you fully interact with them to find all the relevant details.

Solution:
Early in the morning, James Turner drugged Leopold Blanchard in the library and stole a button. Meanwhile, in the tea-house, Ergin Ptoo drugged Gideon Bell and stole a Lemurian seal from the salon. In the salon at around noon, Alistair Koch killed Augustus Vallantine and planted the button on him to frame Leopold Blanchard.