Due to a series of coincidences, Poirot meets his old friend Captain Hastings at the headquarters of an archaeological dig in Mesopotamia where an Arab worker has recently been found strangled. All those working on the dig in the Iraqi desert are either friends or colleagues of the project leader, the renowned American archaeologist Dr Leidner. Tension at Expedition House worsens when the beautiful young wife of Dr Leidner wakes screaming in the night, claiming she has seen a mysterious face at the window.

It is now Poirot's turn to start digging and he soon finds that sexual jealousy, professional rivalry and dark personal secrets abound in the hothouse atmosphere of Mesopotamia.