Who is Walter Trentkamp from Black Friday and what is their importance?

The Federal Bureau of Investigations Eastern Bureau Chief, Walter was friends with Carroll's father. Walter talks to Carroll about his reckless lifestyle. In addition, Walter goes to Carroll's office immediately after his resignation to ask him to reconsider. He succeeds by telling Carroll that lives will be lost without him and that he shouldn't quit because his pride was wounded. While Carroll hates that Walter can see through him, he admits that the older man is right and agrees to stay on until Green Band is settled. As it turns out, Walter Trentkamp is Monsarrat, the terrorist. He says that he has always been with the Russians.