Leave it to Peter Dickinson to dream up something unusual. This British writer creates mysteries that can have all kinds of threatening undertones, and that have an unusual milieu…. Dickinson has imagination, and he also is a sensitive writer. Every new book of his can be approached with anticipation.

His latest is "Walking Dead."… In it he poses an ethical problem. A scientist who is an expert on rat and monkey behavioral patterns finds himself framed for murder on a Caribbean island. The dictator orders him to investigate the potentialities of a new drug. But this time he is not to experiment on animals. He is given a group of blacks who are enemies of the state. Go to work—or else.

This ethical dilemma is the main thrust of the book. But there is another one almost as important. Dickinson skillfully works into the plot the confrontation...