What had Vetinari told Cheery about poisoning?…

What had Vetinari told Cheery about poisoning? ’ You put it where no one will look at all …’ Vimes realized he was still staring at the book. There wasn’t anything there that he could recognize. It must be a code of some sort. Knowing Vetinari, it wouldn’t be crackable by anyone in a normal frame of mind. Could you poison a book? But … so what? There were other books. You’d have to know he’d look at this one, continuously. And even then you’d have to get the poison into him. A man might prick his finger once and after that he’d take care. It sometimes worried Vimes, the way he suspected everything. If you started wondering whether a man could be poisoned by words, you might as well accuse the wallpaper of driving him mad. Mind you, that horrible green colour would drive anyone insane . .