As always, Nero Wolfe and Archie Goodwin are the main characters. Stout had been developing them for two decades, yet in The Black Mountain he finds much that is new to say about them. The familiar elements of their personalities and interaction remain: Their constant bickering does not obscure their mutual esteem, loyalty, and interdependence. But this is the only novel that takes either of them abroad, and the setting generates unprecedented tensions even as it brings out latent strengths and weaknesses.

Nero Wolfe has always depended on his incomparable brain to make his way in the world, and it serves him well in this extraordinary set of circumstances. He relies on his fluency in several languages, his grasp of history, customs, and current affairs, and his knowledge of human nature to get them through the innumerable difficulties they face in New York, Italy, and Montenegro. The return...