Jerry Speir points out that the novel departs from the formula of the Hercule Poirot series. The novel is not set in the manor house or a rural area like a number of its predecessors, nor do the characters represent the British gentry. The villains are a gang of international criminals, controlling a secret, global organization. Their goals include the so-called disintegration of human civilization. They control an unspecified "scientific force", a weapon of some kind. Speir speculates that they could hold the secrets to gravity or nuclear power.