From the introduction:
Within the Herald of Rain, the massive adventure module of the Empires of the Silk Road, the players are thrown into the heart of this world in a web of intrigue and arcane cataclysm.
In the eye of the hurricane, lies Hasan Sabbah, his Hashashin Order, and their plans for vengeance - which the party became a loose end of and the scapegoat for. To save their own skin, to clear their names, and in the off chance that their intentions are noble, to take down a horrendous threat to the Silk Road in a righteous battle, the adventurers must ride west, city to city - and finally challenge Hasan Sabbah in his lair, the infamous Castle Alamut.
Throughout this journey that takes the players from one end of the Silk Road to the other, the world will move with them. The adventurers will travel through the legendary cities of Samarkand - the occupied crown jewel of Asia; Merv - the city of Merchant Emirs; Isfahan - the last stronghold of the Sultanate; and Baghdad - the home of the Caliph and the House of Wisdom.
During their travels, it will be the party’s duty to piece together the conspiracy of the Hashashin Order in each city - and if the players prove to be capable enough, to stop the string of assassinations that serve this conspiracy.
The party will not take on this journey alone. With the spirit of the Silk Road, the adventurers will travel from one caravanserai to another with a caravan in tow - a cast of companions with unique backstories, interests, and opinions.