The book was first published in 1964. Can you recall any notable historical events in the US at this time? Civil Rights movement, among other things.
You did not think Nero Wolfe would not get involved, would you? Twenty six years ago during the events of the novel Too Many Cooks a young black guy helped the detective and so the latter considers himself to be in debt. Now the guy all grew up, became a college professor, got marries and had a son.
The son wants to marry a white civil rights activist girl who also happened to be very rich. If you think it is too good to be true (I mean the rich part), so did the professor. He came to Wolfe to collect on the debt asking the detective to check the background of his future daughter-in-law. Wolfe is reluctant to do it, but a debt is a debt so he has no choice. Several days later he has to change his task and clear the son in question from a murder charge which completely satisfied the police considering the skin color of the suspect.
The first very noticeable thing about the novel is that the recurring characters - especially the main characters - do not age at all. Wolfe's client grew up and was well into his mature age while both detectives still remained the same: Archie Goodwin is still handsome ladies' man and Nero Wolfe's obesity did not cause him any health problems at all.
I was also very surprised to learn that people consider this novel to be racist. Could this be that I read a different one? Considering the fact that it was written during the Civil Rights movement by the old guy - he was pushing eighties at the time - who also always considered himself a conservative the novel is as progressive as it could get. It is also a good mystery.
It is also very interesting to notice the change in racial attitude of the two main characters. Wolfe was never a racist, even in late thirties. This was probably influenced by the fact that he came from a country where simple people were not much better off than slaves. Archie Goodwin did come out somewhat racist at that time - he is a typical white American middle class guy after all, but even in the early book he had to reconsider his views due to Wolfe's influence. There is no trace of racism in him in this novel.
Times changes since the publication of the first book of the series and so did the themes in it. Rex Stout began using more social commentary in his works; this was noticeable in the previous collection, but this time it is impossible to miss.