The Towers of Silence (1966), the second Peter Ward spy novel by E. Howard Hunt (of Watergate fame).
Peter Ward is investigating the death of a CIA agent in India.
Ward is a realistic kind of spy who relies on tradecraft rather than instinct. He's a hard-headed professional, ruthless, unromantic.
A good spy thriller.
My review: https://vintagepopfictions.blogspot.com/2023/01/e-howard-hunts-towers-of-silence.html