When the exuberant president of Ng'ombwana proposes to dispense with the usual security arrangements on an official visit to London, his old school mate, Chief Superintendent Alleyn, is called in to persuade him otherwise. Consequently, on the night of the embassy's reception the house and grounds are stiff with police. Nevertheless, an assassin does strike, and Alleyn finds he has no shortage of help, from Special Branch to a tribal court - and a small black cat named Lucy Lockett who out-detects them all...