Philip went back to Metropolis and began his search. The letter that he received two days ago was from her Sister Amanda. He knows this because it was her handwriting.
In the letter, she said that she hides additional information about the prophecy that they thought would bring a new light on what he should do when Katherine reaches her Vampire maturity Age. At this age, Katherine's vampire blood will be activated and all the power and weaknesses of being a vampire will start to manifest.
Inside the car, Philip was in deep thought, he needed to acquire this new information since he needed to secure Katherine's safety, as for her studies, it's already been taken care of, Philip already decided to recruit Katherine in the Organization, the Organization already knew about her identity.
