Inspector Alleyn’s old school chum, the "Boomer," is now president of the new African nation of Ng’ombwana. On an official visit to London, the Boomer insists that Alleyn handle his security; a difficult task made even more so when the Ng’ombwanan ambassador is killed. Happily, not only is Alleyn up to the task, but he is assisted by a cat who proves remarkably adept at finding clues.