Who is Dr. Edward Berkmann from Mortal Fear and what is their importance?

A noted neurosurgeon and the man behind the killings, Berkmann continues to elude police until he sets his sights on Harper's wife, Drewe. Berkmann is born to siblings, Catherine and Richard, who were encouraged in their incestuous relationship by their mother. Their father had come to America where he practiced medicine until killing himself after the market crash of the 1920s.