Hallowe'en Party discussion

Maybe I'm stupid, or hopelessly unobservant, but I don't know what the four words were that Hercule Poirot wrote on the piece of paper he showed to Miss Emlyn(?).

Hmm... it's been so long I've read it I can't remember. Do you remember about where in the book it happened? (I have a copy so I could see if I can find out!).

And "where" it happened I mean story-wise. Was there any part you remember that the story was headed so I could help you out and seek out that part of the book?

Water was one.