On a scorching hot day in July, 2010, two Panamanian policemen set off in a motorboat from the ramshackle town of Bocas del Toro on Panama's Caribbean coast. It's a bustling place and a favorite of American expats who like to party, occupying an uneasy space between surfers' hangout and drug den. It took the policeman around forty-five minutes skimming over the glassy waters of the Bocas del Toro lagoon, evading clumps of mangrove, to reach their destination: a large, modern house set back from the shore, surrounded by impenetrable jungle.

It turned out that the owners of the house, an American couple calling themselves "Wild Bill" and Jane Cortez, had left in a hurry. Tipped onto a bed was a pile of documents, including a check books and ATM cards that didn't belong to either of the Cortezes. The policemen found a jar containing gold dental fillings and crowns and ammunition for an AK-47. A path at the back of the house led through green, dense bush to a clearing. Someone had dug a couple of ditches, each around six feet long. They were shallow graves containing the remains of five bodies.

Arrested several weeks later, "Wild Bill" Cortez, 30—real name William Dathan Holbert, from Hendersonville, North Carolina—admitted to killing the people buried behind his house, including its former occupants, the mysterious Brown family. Four of the five were American expats; later, Holbert confessed to having killed yet another American expat, making a total of six murders. Meanwhile Jane Cortez (real name Laura Michelle Reese), a couple of years younger than Holbert and also from North Carolina, denied all knowledge of the crimes.

Following the gruesome discoveries, Holbert and Reese's former neighbors, many of them originally from the United States, were split: Some thought the story of the murders should be told, but other refused to speak about it, brusquely rejecting enquiries. From her jail cell, Reese refused Nick Foster's interview request. But Holbert agreed, with surprising enthusiasm. In 2014, Foster entered the jail where Holbert was being kept in advance of his trial.

In March 2014, I made my first visit to the city of David, Panama. William Dathan Holbert and Laura Michelle Reese had passed through here in 2007 and hadn't lingered. But since their Panamanian crimes took place in the west of the country, and David has its only big courthouse, the pair had to await trial in jails in the city. A newspaper reporter covering the crime beat in David introduced me to Demetrio Abrego, a Panamanian TV reporter working out of an office of the TVN channel covering western Panama. Ábrego had interviewed Holbert in his cell six months previously. It was a weekday, mid-afternoon, and Ábrego had just filed that day's story with the channel's HQ in Panama City.

The Cortez house, behind which five bodies were buried.

A dark- eyed man in his forties who describes himself on Twitter as a "Journalist, Lawyer, Teacher and Farmer," Ábrego was relaxed and expansive. A half-dozen watercolor caricatures, widemouthed, bug-eyed—one for each member of the TVN team working in David—stood on a shelf in his office against a wall whose paint was peeling like a bad skin disease. I mentioned to Ábrego that I planned to ask Holbert for a meeting. Ábrego's tone changed. He recalled going into David prison with his camera team, feeling the stares of the prisoners in the exercise yard, and entering Holbert's dark, stinking cell. Once the interview was done, a couple of younger members of the television crew took selfies in the yard with Holbert, much to Ábrego's displeasure. Selfies with the American prisoner would only serve to shore up his notoriety among the other inmates—surely the reason why Holbert was happy to be in the frame. With his smiles and back-slapping, Holbert had—on some emotional level—won over those junior crew members. But he certainly hadn't won over their boss.

"Don't trust anything Holbert ever tells you," warned Ábrego. "He is the ultimate manipulator."

A prison guard strolled across the empty yard and escorted me and Claudia Alvarado, Holbert's attorney, to the administrative wing of the jail where he was being held. Three chairs had been placed in the narrow space in front of a counter, behind which four or five young women were processing stacks of paper files. Behind them I could see the number 1,124 written on a board on the wall—the number of men locked up in David prison that day. Guards shuffled in and out. We were in an exposed place, but we were entirely ignored.

The deck of the now-defunct Jolly Roger Social Club, which Holbert owned and at which he met most of his victims.

Holbert arrived with a smile and a brisk "Hey, I'm Bill," and offered his hand. He sat next to Alvarado on an identical, straight- backed chair. He wore no handcuffs and was not, as far as I could see, restrained in any way. I faced Holbert, sitting lower down, in an armchair. He was wearing baggy shorts that extended past his knees, a yellow t-shirt, and a large crucifix made from two pieces of wood tied at the center with a rubber band. He looked physically fit though pale, and had a goatee. I tried to put to the back of my mind the thought that the finger that pulled the trigger to take the lives of at least six people had just squeezed my palm.

"Do you think much of your life back in the States?"

No, Holbert preferred not to think of the life he had led before prison. In high school, he said, he had played everything except basketball. He had played defensive end on his high school football team. On top of that, he had done wrestling, boxing, and the discus and shot put. He said that he had been class president, which I knew was untrue—he had been almost perfectly anonymous at North Henderson High. I could have confronted him about this, but I chose not to do so. The world is full of liars and fantasists. But it's not full of multiple killers. Better to move on. We talked about his life after graduating from North Henderson. Holbert leaned forward, resting his chin on his thumb and forefinger. He looked me in the eye all the time, but now his stare was deep, borderline aggressive. A narrow shaft of sunlight picked out particles of dust, rising and falling.

I wanted to talk about the period when Holbert and Reese set up a white supremacy bookshop.

"I made a gain every month. I sold heavy equipment. I was working eighteen hours a day. But I fell apart after my divorce. I said fuck it and left.

"When they took my children away from me, I became a different man. I appealed, and lost. They put the same judge there. I played the game by their rules and lost. I was really pissed off about the States."

"It was a kind of tipping point?"

Holbert looked at me quizzically. I said, "You know, like in chemistry class, when a piece of litmus paper turns from pink to blue. It happens in just a moment."

"Yes!" said Holbert. "I didn't want my house of cards to fall down. I had six houses. It was an empire!" But things started to unravel for him. "I robbed Peter to pay Paul." Holbert had been looking past me, but then concentrated his gaze. "We are brought up thinking that money is everything!"

I wanted to talk about the period when Holbert and Reese set up a white supremacy bookshop in Forest City, North Carolina. About how Holbert took to the street with a megaphone to get people to attend his meetings.

"That was nothing to do with racism," said Holbert curtly. "It was anti-immigration." He wanted to move on from that line of questioning: "I don't think about my life outside anymore. If I did, I'd go insane."

What about the families of his victims?

"I feel horribly. I killed innocent people. I killed my friends."

From where I was sitting, Holbert's contrition felt not at all convincing.

"It was a bad decision from a moral standpoint. Ridiculously bad. I don't know why I did it." So why did he kill Cher, for instance? "I wanted to show myself I'm a coldhearted bastard. I went against my instincts. I don't know why I did it. Everything was screaming, Don't do it! But I did it anyway. I killed my friend.

"It's all my fault, all of it. I am your worst nightmare.

"But I'm pragmatic. I want to heal the past. I'm interested in the future. I work with the Catholic Church. It's a karma thing. I lived a shitty, selfish life and I want to make up for it."

I asked Holbert: "What would you say to people who think you deserve to die for your crimes?"

As quick as a flash: "What people?"

"Some people in Bocas, for instance. It can't be a surprise to hear that there are folks who think you deserve to be put to death for those murders."

Holbert shook his head like I was missing something really obvious.

"I feel horribly. I killed innocent people. I killed my friends."

"Back home the best you can expect—the best—is not to get out of prison again. In America we have to punish, take a sledgehammer. But here it's a more forgiving society. They're not judgmental. Life is laid- back. I'm not an American anymore. I feel half Panamanian. They [Americans] make me want to vomit! The US mentality makes me sick. But Panamanians are more intrigued than shocked. They want photos and autographs." Holbert brightened. "I love it here! Here, chicks call me!" The man facing me was animated.

"In America they think of me as Hannibal Lecter or Charles Manson. I'm infamous. But here I'm loveable. I speak ghetto Spanish. I'm Bill, nobody special." Holbert said that in North Carolina nobody could believe he had turned out this way, that this was the man they had known. "There's a stigma," he said.

"I've done some cool shit and some bad shit. No one wants to be a mass murderer."

Darklands, a remote part of Bocas del Toro and the location of The Jolly Roger Social Club.

Holbert turned to Alvarado and said: "El panameño está más interesado que asustado." Panamanians are more curious than afraid.

Alvarado nodded her head.

An hour had passed, and the prison guards were bustling all around us. The typists behind the counter were filling out forms. It seemed we could stay here on these rickety chairs as long as we pleased.

"Now I read a lot. They sent books [to the prison] from a library that closed in the Canal Zone. They're mainly textbooks. It's not a curriculum. I like the ones on anthropology." It turned out that Holbert was writing some books of his own. He counted them on his fingers. There was an autobiography ("I think it's pretty good") and also what Holbert described as a "parable."

"You've read The Alchemist by Paulo Coelho? Well, it's a bit like that."

A third book was going to remain a secret for the moment: "There's another one, but I don't want to talk about it."

I had started to feel nauseous. But there was still one big question I wanted to raise. It was in my note pad, circled. I was thinking now of a photo in the DA's file of a family scene. Ever since I saw it for the first time, I could not get this photo out of my mind. The image was of Michael Brown and his wife, Nan, and Brown's sons Marco and Watson. Watson was sixteen or seventeen when the picture was taken. He was seventeen years and two months old when Holbert put a gun to his head and pulled the trigger. The photo was taken by Brown's daughter in the muddy yard of the Brown residence in Darklands. I have a black- and- white copy, although the original was almost certainly in color. I can imagine the blue of the sky at the corners of the picture, the green of the banana leaves in the background. With the colors drained, the life has gone, too. Marco, on the left, long- limbed, exudes a boyish confidence. In the middle stand Michael and Nan Brown. Watson is on the right of the photo, next to his mom, shy, squinting slightly, locks of hair falling over his eyes. He is, I imagine, small for his age. Probably when folks looked at him and imagined how old he was, they guessed a year too few.

A storm hits Bocas del Toro.

"How do you kill a seventeen-year-old boy?"

Holbert looked like this wasn't a question he was expecting.

"How do you kill a seventeen-year-old boy like Watson Brown? Tell me, how exactly do you do that?"

Holbert said he was following orders. It was that old Mafia story again: "They said, 'Take care of this.' It's what happened. The kid, he was there. I ran out of money. I'm not justifying what I did. . . . And they were people trafficking, the Browns. They were doing some real bad shit. The boy,

too. . ." I thought I heard Holbert say that the Browns were killing and raping. But I felt sick and suddenly I realized I wasn't hearing right. I put my pen down. I thought of a disinfectant gel I had back at my hotel that I wanted to rub into my hands and arms. I needed to get out of this place.

One more time, now a bit louder, and in a different tone, despite myself: "How do you kill a seventeen- year- old boy? How is this possible?"

Claudia Alvarado, Holbert's attorney, fired an inquisitive glance in my direction. For me, the conversation had ground to a halt right there. I now felt like I was about to vomit. But Holbert had moved on to talk about other things.

"It's going to be an interesting ride. I'm not beaten. I'm not going to lay down and die.

"Before I'm forty I'll be out. There are just too many loopholes."

Excerpted from by Nick Foster, published by HENRY HOLT AND COMPANY, LLC. Copyright © 2016 by Nick Foster. All rights reserved.