Mason rushes into the house to get a document which he forgot to pick while going to the office. He could have just sent Dennis to get it for him or any of his workers under him but he wanted to come get it himself because he wanted to see Bella. Bella is working as a Personal Maid to Clara and he wants to see her working and lamenting on her unlucky self.
Mason goes up to his room and picks up the document. On his way up, he didn't stumble on Bella even though he wished to. No one knows he is in the house including Clara, she doesn't know he has gotten back to the house. Mason walks out of his room and stays at the doorway. Should he go round and see, maybe he can see her passing by? She may be in the kitchen so should he go there? Mason waves the thought off his mind. He may want to see
