Seraphine looked very serious with her words. She wanted to make Imperial much better after what Darco had done. She didn't want Imperial to fall into the hands of someone like Darco and his mother.
Because that would be the beginning of Imperial's destruction if Darco actually became an Emperor.
"Someone has to stop him before something worse happens. And I think, I am the one who will do that!"
She went on to say some of the things she would do to the Imperial later. From all of that, Harvey thought that what Seraphine was saying was really serious.
What she was saying was that she wanted to make Imperial better and restore its former stability.
But Seraphine's original goal had not changed, she wanted justice and her mother's and Dominic's names cleared.
