hallo friends,i have a question about 'big daddy' and 'little sister' in bioshock.my friend is playing bioshock now and i enjoy watching it,but i have not yet clearly understood what we are supposed to do with 'big daddy' & 'little sister',my friend is a very kind person and he never hurts a 'big daddy' as it would make a 'little sister' helpless & orphan and hurting a little sister is out of question,we both love little sisters very much.can anyone give us any idea what we should do with them?