[hedaikes]

Which mission is it, who are you assassinating? I have no idea what you're talking about and I beat the game a few times.

Maybe he's talking about finding a guy/meeting in a certain place, in order to carry out an assassination you have to complete some of the tasks it asks for. Like pick pocketing, eavesdropping, interrogating, etc etc. The more info you have the better.

So maybe you just have to carry out a couple of those missions first before a certain "lookout" or place to complete the mission become apparent. If you could say which assassination, town or memory block your on it would really help me out in answering your question.