You have to kill the head of a major oil company. He owes you a lot of money, but was not going to give them. You will have to go through all its label to find it. You can help your friend, which you'll see after how to get there by car from the beginning to the first label. As soon as you get there before the last house, where he hides from you with your girlfriend, you have to kill them. And only then will you go home with a calm mind and a sense that you do your duty.