In one of Rex Stout's most famous early mystery novels, Too Many Cooks, Nero Wolfe was aided in the solution of a murder by a twenty-year-old Negro.

Now, in A Right to Die, Stout's 1964 novel, this same Negro is a man of forty-five and a professor of anthropology.  He comes to Nero and to Archie Goodwin with a pressing problem concerning his son and a young, beautiful, and wealthy white girl. Both the son and the girl are active in a civil-rights group.  Their entanglements with each other and with the group lead to two murders, and Nero and Archie, in their search for the murderer, become fascinatingly involved in America's most immediate domestic problem. They unearth a murder motive unique in mystery fiction, and encounter some of the most interesting people ever invented by the master of the modern mystery, Rex Stout.  Published in 1964.  synopsis source:  nerowolfe.org