Head over to the right of the starting point. Go over to the post and look down. You will see 2 people holding up a merchant. Take them out with some Phantom Blades or a quick Aerial Assassination and then fighting the remaining person. Interact with the merchant and he will start moving.
Follow the merchant as he moves into position. Keep with him as he moves through this area. First, stay on the right-hand side. There will be 2 Extremists waiting a bit down the road. When they take notice of the merchant, move in and deal with them. There are 2 more pairs that will come after you. One of the other. Take them out and the merchant will be able to get into position. After 90 seconds, he will start sending up the fireworks. This works to provide a great distraction for you.