Perseus accidentally killed his grandfather, Acrisius in a discus throwing contest and fulfills the Oracle prophecy.
Marcus and his father are arguing about whether the cops are doing a good job or not. Marcus believes that the cops haven't caught any terrorists, and they are just making people scared. Marcus's dad on the other hand, he strongly believes that the cops are doing amazing work. Marcus's dad even said he would gladly be pulled over if it was to make him feel safer. Marcus and his dad have opposite outlooks, and this is the big conflict.
Hope this helps! :)
