Among the rose-red cliffs of Petra, a touring family draws the eye of everyone around them. At its centre sits the elderly Mrs Boynton, a former prison wardress who rules her grown stepchildren and daughter with a calculated, suffocating cruelty, keeping them isolated, fearful, and unable to imagine a life beyond her control. Watching the family unravel are a young doctor, Sarah King, and a French psychologist who recognises the matriarch's tyranny for the sadism it is. When the party reaches the ancient city, Mrs Boynton is found dead in her chair, seated apart from the others, an apparent victim of the heat and her own failing heart. Hercule Poirot, travelling in the region, has already overheard a single chilling sentence spoken between two of the Boyntons, and he is certain the death is no accident. Given a narrow window by the local authorities to reach the truth, he sets out to question every member of the party and to reconstruct the exact movements of an afternoon in which almost everyone had reason to wish the old woman gone. The investigation turns on small contradictions of time and testimony, and on the psychology of a household shaped by years of domination. Poirot must separate the relief of the freed from the guilt of the killer, weighing motive against opportunity in a setting as confining as the family itself.