The Gatekeepers. Bruce Highland, #1

A Private Investigator, Bruce Highland, a former Military Intelligence Agent, is working on a case to clear his client of a murder charge. His investigation leads him to a secret society (The Gatekeepers) that actively manipulates the government, aided by layers of rogue agencies and corrupt leaders. In addition to ultimately clearing his client, he manages to avert a major armed international conflict in the course of bringing justice to the corrupt intelligence agents that were responsible for the murder for which his client was accused.
Primarily set in the San Francisco Bay Area, Highland's adventures take him across the country, and internationally to Central America and the Caribbean islands.