The book was apparently written after the troubled year of 1968, which saw the assassination of Martin Luther King Jr. and of Robert F. Kennedy a few weeks later, as well as political turmoil and anti-Vietnam demonstrations in the United States.

He is inserted into an operation currently being carried out by a rival government agency, one that is trying to thwart Communist plans to obtain secret information about a major American-Canadian security project called the Northwest Coastal System.

A man named Grant Nystrom has been recruited by the Communists to take delivery at five different points of microfilms of the project as he travels through the Northwest and into Alaska playing the role of a dedicated fisherman.

As usual, there is a two- or three-word final paragraph: And as in many of the books, Helm also finds time to reflect on the deficiencies of Detroit automakers: "Even commercial vehicles are encumbered with a lot of Mickey Mouse gadgets these days — that big, rugged, powerful truck engine was decorated with a cute little automatic choke, for God's sake!

One feature in The Interlopers that is not a standard Hamilton plot device occurs on page 175 when, for one of the very few times in the series, the super-competent and super-foresighted Helm falls into an enemy ambush that he had not planned for or anticipated.