Who is Thaddeus Red Beaumont from Ninth Key and what is their importance?

Mr. Beaumont is a real estate developer. He owns Beaumont Industries, Inc. After his wife death, Mr. Beaumont's health declines, and his brother Marcus steps in to run the business. Beaumont experiences episodes when his ideas are not based in reality. He thinks he is a vampire and believes himself responsible for the killings of certain people. Susannah must investigate the truth behind Mr. Beaumont and his family.