Answer:
the motivation for the crime.
Step-by-step explanation:
Tony Hillerman was a great American writer. His works are described as detective novels, with compelling narratives, full of suspensions, with surprising twists and plots that are very well elaborated and explained.
Their stories generally revolved around a crime and Hillerman had an incredible talent for explaining the reasons that made this crime happen, the motivation of villains to do such acts and that was exactly what made their stories so memorable.