(I'm just winging it. I don't really know what goes on with the Prince. But if I need to change this post, let me know.)
After a glorious brunch in the midst of his private sanctuary, Edward laid in the sunlight not afraid to let his skin shimmer with the colors of a rainbow. That was just another little quirk of his that he didn't want to let anyone else know about himself. He laid there thinking about how the Prince's actions were becoming more and more hostile towards the humans. He knew what the Prince was thinking at all times and it repulsed him.
To the Prince, humans were nothing more than little play things and dinner. They had no significance and no say in anything that went on in their lives when vampires graced them with their presence, even if it were just to feed off of them. He was having a clash of conscious.
On the one hand, the Prince took Edward in when he had no idea what happened to him and that was back in 1918. On the other hand, Edward wasn't one for setting aside his values and beliefs regardless of him being a vampire. And this was why he kept his most dangerous of secrets to himself.
He was having problems trying to justify the things that the Prince did to humans. He knew that humans- though they were a violent and some times destructive species- deserved nowhere near the kind of treatment that the Prince dealt when he interacted with them. It was already eating Edward up when he had to bring people in for the Prince to feed off of but the sounds of their screaming at the realization of their imminent death made Edward wish that he were death.
He returned to his quarters at the castle and played his piano. It was his form of therapy and it always allowed him to talk about his problems without having to worry about anyone figuring it out. He sat at his baby grand piano, lifted the key cover and played his thoughts to his cold dead hearts content.