The next morning arrived gray and humid, with the kind of oppressive Louisiana heat that made everything feel like a fever dream. Ferdinand stood in his chambers, staring at his reflection in the ornate mirror that had belonged to his mother. In an hour, he would either be complicit in mass murder or gambling his life on Isabella's political strategy.

He'd chosen his clothes carefully—formal enough to show respect for his father's authority, but not the ceremonial robes typically worn for ...