. . . and it makes me sick"I was thinking - We're led to believe that the note is referring to the murder of Gabby's stepfather. However, that could just be a red herring that causes the women to run around, trying to cover up. The note could be - I know what you did, you failed to return that library book and didn't pay the library fines. I know what you did, you didn't stop at that stop sign. I know what you did, you used margarine in that recipe instead of butter . . .