While traveling through the Orient, Hercule Poirot stopped in Jerusalem. One evening, standing by the open window of his hotel room, he suddenly heard a voice say, 'You understand she must be killed, don't you?' At first, the detective didn't pay any attention to these words. But he was soon forced to remember them when his hotel neighbor, a wealthy elderly American woman traveling with her family—her daughter, son, daughter-in-law, and grandchildren—suddenly died. Poirot learned that in life, the deceased, a former prison warden, had been a true family tyrant. The great detective was at a loss as to who killed the old woman. And was it even murder? After all, there were no traces left. Meanwhile, Poirot had only a day to solve the mystery.