Help ? in's Creed?

Thanks for previos answers but no joy!!! I'll try to explain more. I'm about 3 hours into playing and while in Jeruselum I've recevied a mission. I've climbed all towers and save all citizens etc. but there is no sign of the marker for my new mission. Damascus, Jerusulum and Acre are all marked with a cross on exiting but I can find no mission in each of the towns. I went back to the Master but there is no mission there. I tried the Knigdom but no good. Any ideas?