This is book 10 of the "Nero Wolfe Continuation" series.

This note contains spoilers for the book.

Archie is shot at in front of the house, and they receive threatening phone calls. Also a client turns up who is being blackmailed with pictures of her hugging (or perhaps slightly more?) a rich Italian guy.

Wolfe figures out these two are related, but we aren't given any clues to how. It's not very honest, I don't think. And Archie's vocabulary remains an issue; Goldsborough can't seem to get the hang of that.