Black Cherry

The invasion of New York was brutal. The terrorist group Bakudan invaded the state and held the citizens of a whole state hostage. Over 5,000,000 people were dead by the time American forces finally pushed them out. But that wouldn't have been possible without the spy named Black Cherry. No one knows who Black Cherry is, but whoever it is saved hundreds of lives.
But years have passed since then and Volt really doesn't want to do her report on the invasion of New York. Why was history such an important subject anyway? But she has to, so she cracks open her grandmother's diaries from that time. She wasn't happy to read about what her grandmother went through during those three years that terrorists ruled New York, but something's not adding up. Her grandmother is acting weird the further and further she dives into the diaries. What is going on with her?