Assassin's Creed 2 Walkthrough

After parting ways with Leonardo, break into the walled-off area to the northeast and trigger this mission via a waypoint on the parapet walk. After the cut scene, you need to trail a courier that zigs a zagging path through the city. Stay far enough behind him that he doesn't get curious, but also be sure to keep him in your sights. If he gets separated from you by a wall, a countdown timer hurries you to catch back up.

Occasionally the target will stop and look behind him to make sure no one's following. Don't worry too much about getting spotted as he doesn't become suspicious instantly. If he does see you, just turn away and walk further from him until the courier gets back to walking. After hitting a checkpoint, the courier crosses through a line of soldiers and if you try the same you'll be instantly spotted. From here, you need to take to the rooftops.

The target eventually goes through another line of soldiers, at which point you get a quick break by way of a cut scene. After the scene plays out, you need to secretly infiltrate the building and kill the courier to steal his outfit. Climb the face of the building and, once you reach the top, look to the right. There's a pile of hay you can dive into on the ground level. Jump in!

Hop out of the hay just long enough to get the attention of the guard on the ground level before hopping back into the hay stack. The guard will wander over to inspect, which lets you get a silent assassination from your hiding spot. With that guard taken care of, you can waltz behind the target ahead and assassinate him to steal his rad outfit and end the mission.