Allan Pinkerton is a private investigator. You receive a letter from Jeremiah in which he suggests you to hire him. Sadly, his offerings are quite expensive - 1000$ per month but if you make him a favor you will receive a discount. The money must be transferred to agency account in any bank.
The favor is a simple quest in which you must transport the investigator's five agents to the appointed cities. For that you receive a 50% discount. You must complete this quest.
The detective must be paid every month, the transaction can be done in any of the banks. If you are late with payment then Allan won't be working for you until he gets the money. His task is to inform you about your opponent's actions allowing you to act sooner. This is done by completing special quests whose goal is to prevent your enemy from getting additional stocks.