“If anyone deserves to die, it’s these guys,” Carl Mueller, Kayla Mueller’s father, told me. It is hard to convey how twisted the ISIS kidnappers were. They collected hostages for reasons that could fairly be called psychopathic. They abused them recreationally. They raped female hostages, including Mueller. And they taunted the families of their victims—demanding enormous sums of money, or prisoner swaps, with full knowledge that the only outcome of this process would be the death of those families’ children. ISIS never even revealed the burial site of the victims’ remains.