In this second and last volume of the Sani' al-dhalam series, Youssef continues the journey that had started with the interview of a university professor, Magdy, convicted for the murder of his own son. Magdy had revealed that his son was alive, and asked Youssef to find him and kill him. Here Youssef finds himself chasing a mysterious entity known as 'the Thing', which has existed since the beginning of time, and is preparing for the worst and darkest period of our history. Unfortunately, however, the Thing knows Youssef is looking for it. The Twenty-third night is the night of their ultimate confrontation.