Who is Howard Orton from The Last Thing I Remember and what is their importance?

Howard Orton is a member of the Homelanders. He claims that Charlie is a Homelander, and that he has always been on Charlie's side. The Homelanders, by definition, are Americans who've been recruited by the Islamists to destroy America from the inside out.

Howard is a strong adversary and manipulates Charlie in order to complete his mission, which is to blow up the bridge when Richard Yarrow, Secretary of Homeland Security, is crossing. Charlie thwarts his plan by blowing up the bridge before Yarrow reaches it.