This is a Hercule Poirot Mystery first published in 1936.
The setting for the story was in Iraq where an expedition of men and women were gathered together led by an American archaeologist Dr Leidner in some excavation work. The lovely Mrs Leidner felt unease staying in the living quarters fearing that someone was out to kill her. Was it a case of mental sickness for Mrs Leidner to feel that way? Nurse Amy Leatheran was engaged by her husband to take care of Mrs Leidner.
This story was narrated by Nurse Leatheran based on her perspective of her encounters with the various people in the expedition. Hercule Poirot happened to be passing through the Iraqi town and was brought into the picture when a murder happened. The way the victim died was unusual and baffling since no one had seen any stranger going into the living quarters during the time of the murder that was during broad daylight. Was the murder carried out by a member of the expedition?
Hercule Poirot had to establish how the killing happened and who had the motive to kill the victim. The breakthrough in the investigation could only happen when Poirot knew how the killing was carried out. The killer was then brought to light from then on.