
my theory is he sees her as the bug(something he wants) and he will eliminate anyone who gets in his way. That includes her brother. She’s just like the watch, the pen, the bug, he’s found of it but it’s not his. He had to go through obstacles to obtain it. (killing, manipulating)
I have a feeling the detective is going to die or the brother. And it will send her in a spiral and try to kill herself. and that will make him upset.