Who is Brian Shaw from Night Probe! and what is their importance?

Former British secret agent, Brian Shaw (alias) is retired and supposedly dead. He meets Mrs. Huston at a funeral where she slips an envelope into his pocket. The note summons him to London for a meeting, where he is given the assignment of watching the Americans in regard to the North American Treaty. Shaw travels to Washington, then Los Angeles, where he meets Heidi Milligan, who becomes his lover. Their relationship allows him to easily obtains the information he needs regarding the North American Treaty.