When we return to the army camp after the weekend, Model and I walk a hundred yards up the road to the cemetery of freshly dug graves for the slain refugees. Inside the low brick wall, rows of white crosses bear only the victim's dates of birth and death. One reads "2002–2004." From a nearby school, a chorus of children reciting lessons sounds like a choir of angels.

We pile in the army trucks and drive north, paralleling the Rusizi, to the Kiliba border post. The Democratic Republic of the Congo is 30 yards away. I walk down to the river to look for Gustave. As I'm glassing the banks with binoculars, hysterical screeching and ululations from across the border freeze my blood.

"Michael!" Munie calls to me. "Come on! We have to leave."

The Congolese border guards are Mai Mai, the storied "magic warriors" of central Africa. They anoint themselves with supernatural water before going into battle, believing it will render them invisible to their enemies. (Mai Mai literally means "powerful water.") There are stories about them wearing water-related paraphernalia such as shower hoses and drain plugs as protective talismans. They're suspected of participating in the refugee massacre, and I can believe it. The mere presence of Tutsis in our escort is enough to provoke them.

Yes, I concede, coming to my senses, it is time to leave. We will not find Gustave, but our conversations with his victims and with Faye have taught us a good deal about him and his habits anyway: He is a killer, a survivor, and probably as big as Faye believes him to be. But he is not the reigning beast of chaos in Burundi. Ethnic conflict is.

"The biggest crocs I've ever seen have been in communist nations or countries at war, places like Cuba, Burma, and Cambodia," Barr told me before flying out. "They have survived because people have other things to worry about. If peace ever comes to Burundi, mark my words: Someone is going to kill that animal."

Until then, Gustave lives.