In this story, the great (in several senses) private investigator Nero Wolfe takes on the FBI (the United States Federal Bureau of Investigation). His client, Mrs. Rachel Bruner, has been harrassed by them because she sent out hundreds of copies of a book critical of their organization (THE FBI NOBODY KNOWS) to very influential people. She hired Nero Wolfe to get them to stop it. He thinks it's futile and tells her so, but she appeals to him saying that he is the onlyo ne on Earth able to do it. Before it is over, Wolfe and Archie Goodwin are likewise being followed and are mixed up in findking the killer/s of a reporter who was writing an article, also critical of the FBI.
This is a very odd mystery but a very interesting mystery story. Nero Wolfe is a master manipulator in the interest of truth and justice, although his methods are VERY unorthodox. This is one of Stout's best.