The Ghosts of Saigon

Private detective Gabe Treloar would never have gone to a reunion of his Vietnam unit if there hadn't been a note of incongruous urgency in Mitchell Queen's invitation. He learns why when Queen, now a successful movie producer, tells him that a particular nemesis of theirs has surfaced after disappearing twenty years ago: Martin Starr.
Starr was a criminal then; he is still. He has turned up in California and is threatening the actors in Queen's current production, a story set in Saigon/Ho Chi Minh City. Queen is desperate to get Starr out of his life, and so he turns to Gabe for help.
Teaming up uncomfortably with the enigmatic private eye Connie Armijo, Gabe follows Starr's trail to 'Nam and to a dramatic climax in the California hills.