Stuck on Assassins Creed 1!!?

I'm at the part where you have to the three different guys all at once, one in Acre, one in Damascus, and one in Jerusalem. I went to the Assassins Bureau in every city and went to every view point, but i have no objectives! So i have no idea where to go or what to do! I heard you have to go Damascus first, but that still didn't change anything, & i completed everything in that town! I also heard that if you go back to Masyaf, that you would get the option to fast travel somewhere, but I never got that option! PLEASE HELP!!