The Black Mountain

When Nero Wolfe's longtime friend (the restaurant owner Marko Vukcic) is murdered, he and Goodwin begin an investigation that eventually takes them to Vukcic's home country of Montenegro. The mystery itself is underwhelming and the image of Wolfe trekking across Europe is unrealistic, but it offers one of the few entries in the series where Wolfe not only leaves his 35th Street townhouse but actually has to work.