“Does the moon ever get tired of following us, Papa? Or is it just keeping an eye on the sunflowers?”

Ten-year-old Leo stood in the center of the Aldridge garden, his hands tucked into the pockets of his linen trousers, his amber eyes—so like his father’s—tracking the silver crescent hanging over the Sierra Madre. Beside him, eight-year-old Aria was busy trying to convince a golden retriever that a crown made of jasmine was a mandatory fashion accessory.

Lucian Aldridge, now in his early forties with faint, distinguished silvering at his temples, sat on the edge of the stone fountain. He watched his son with a quiet, profound intensity. The “Iron...