Hmmmm My cat is being rather strange....?

Hey everyone... Every morning for the past 4 weeks my siamese cat waked up 5.00am (exactly) and starts crying REALLY loud.. If anyone has a siamese or knows how loud they cry then you know what i mean.. sounds like a baby crying... I even tested him once.. I put my alarm clock on for 4.45am and dead on 5.00am i hear him jump off my mums bed and starts the crying IN THE HALLWAY! I get quite scared... do you think it could be a ghost... or.. i dont know?.. really stuck on this one.. and hes a very very intelegent cat he wouldnt just do this for no reason.. so something is obviously disturbing him... :S xxx