This is book 31 of the "Nero Wolfe" series.

This note does not contain major spoilers for the book.

Nero Wolfe books seem to be my fill-ins at the moment when I'm not sure what I want to read. For books this old I'm a bit more lenient about spoilers -- I don't say who did it or give away any big surprises, but some information may leak through.

This was an excellent one; though I'm inclined to think they went from believing nobody could have slipped poison into the drink to accepting that somebody had done so rather too easily. (The issue of knowing who would drink the drink was well dealt with, anyway).