The Dead Zone - C. D. Moulton - Bog

Large print for those whose eyes are as bad.
Dr. Sommers is researching rituals of certain cults in Central America. He has made a lifetime study of the practices and keeps meticulous notes.
He is found at his desk. He was writing about an orchid used in certain rituals. It is said that the flower can be made, through certain incantations, to expand and cover the head of a person, thus smothering him.
He died of suffocation. He had also recently run afoul of certain of the medicine people who were involved in those rites.
Det. Lt. Osvaldo Quinteros Perez is called to investigate. He is a specialist in such cults. The place where this happened was in the part of the Indigeno territory he referred to as the dead zone. It is known for deaths connected to those cults.
His friend and fellow cop is Renaldo Estes. They are quite the team.