In early 2014, a 27-year-old Alaskan named Cody Roman Dial embarked on a grand and rambling overland journey through Mexico and Central America. He was the son of National Geographic Explorer Roman Dial, a biologist and multisport virtuoso renowned for audacious feats in mountaineering, ice climbing, rafting, and grueling backcountry endurance races. In Anchorage's adventure circles, Roman is a mythic figure. Cody's odyssey seemed to be driven at least in part by an attempt to carve out his own space in the wilderness.

That spring, after a rafting trip in Mexico with Roman, Cody set out alone and began threading his way southward. He climbed Guatemala's 14,000-foot Tajumulco, the highest peak in Central America. He slept in a gold miners' camp and scuba dived with whale sharks. After a surfing idyll in Nicaragua, he crossed into Costa Rica on July 3. Several days later, Cody emailed his father from an Internet café in a small town called Puerto Jiménez. He planned to hike through Corcovado National Park—a notoriously challenging and dynamic rain forest—avoiding the main tourist trails and flouting the government mandate to hire a guide. On July 10, Cody entered Corcovado carrying a backpack and a crude map, which he had printed off the Internet. Then he disappeared.

For the next 12 days, Costa Rican search-and-rescue teams scoured Corcovado's labyrinth of ravines and fast-flooding rivers. Roman himself flew to Puerto Jiménez to assist the effort, at one point sneaking into the jungle to conduct his own illegal search. Costa Rican authorities suspended their operation in early August but, believing Cody might still be alive, Roman soon called in a team from an Anchorage-based wilderness survival school. The group searched for five days around an area where a gold miner reported seeing Cody—an effort I joined and wrote about for Men's Journal. Ultimately, they found no trace of Cody or his equipment. Roman has since repeatedly returned to Costa Rica to continue the search. His efforts have been documented in the six-part series Missing Dial, airing on the National Geographic Channel, which premieres May 22.

View Images Roman Dial with his son Cody in 1987. Photograph courtesy the Dial family

When we last spoke, you had traveled to Panama to search for Cody, thinking he might have tried to cross the Darién Gap, a notoriously wild stretch of jungle, after leaving Costa Rica. What’s happened since then?

We went down there and there was no record of him crossing into Panama, according to the authorities, no passport record of him going across. But we thought the border is really porous, and it would have been really simple for him to sneak across. And so I flew to Panama City and drove all the way to the last town you can drive to before you can get into the Darién Gap. It was just really apparent it would’ve been extremely difficult for him to get all the way down there. There’s a bunch of checkpoints all the way and so I just decided he didn’t go to Panama.

Later that spring, Paul Lima [director of development at This Is Just a Test Productions] approached [my wife] Peggy and said there’s a possibility of doing a TV show about our search for Cody, and this guy had lost his father in Honduras. Using cameras and the media had really helped him get a conviction for his father’s killer. Peggy thought that sounded like a good approach for us to use to figure out what had happened to Cody Roman down in Costa Rica.

Do you think media attention might help shed light on his case?

When there’s a media spotlight, it calls attention to everyone’s behavior. It makes people more aware of what they’re doing. If you don’t go down [to Costa Rica] and rattle their cage, they’re not going to really do anything. It doesn’t seem like there’s a lot of urgency to figure out what’s going on. But I’m the father, so I do want things to move forward.

You brought in two investigators—a former DEA agent and a retired Air Force pararescue jumper (PJ). Was this to continue searching in Corcovado National Park, the last place Cody was seen alive?

I came to the conclusion that Cody wasn’t lost in the jungle. He had been killed or kidnapped. I needed someone who could go around and ask questions and know what kind of questions to ask. We went back in July 2015, spent six weeks, and then I went back in November and January [2016] and then again in March.

Missing Dial Trailer National Geographic launches a covert investigation into the disappearance of adventurer Cody Dial. Missing Dial premieres May 22 at 10/9c on the National Geographic Channel.

Walk me through what happened once you were on the ground.

Carson Ulrich is a retired DEA agent who worked in Latin America for 25 years and speaks Spanish. He's a big, intimidating guy. Ken Fornier is a retired PJ and easygoing. When we got there, they started snooping around and interviewing people I had talked to before—Jenkins for example [the gold miner who reported seeing Cody]. And then we spent some time with the OIJ, the Costa Rican FBI, and at the American embassy.

What did you find out?

We were able to piece together that Cody had gone into the jungle and then come back out. Cody and this character, Pata de Lora [which translates to "parrot foot"], traveled back to Dos Brazos together. A couple of people had seen them. Carson and Ken retraced that path by engaging some informants who traveled through the mining camps to piece together what else happened. It all seemed to center around this trip that Cody had taken after he had come out of the jungle.

Pata de Lora's name figured in the case early on. He told police he guided Cody into Corcovado, but you initially dismissed him as a suspect, partly because locals reported seeing him smoking pot with a gringo, which wasn’t characteristic of Cody. What changed?

Cody consistently said I don’t want a guide. The second thing was the timing was off—all the dates that people gave about when they saw Pata de Lora were a week late. Those things made me think it was a different person. I dismissed it given what I'd known. As for the pot smoking, I’d be surprised.

Soon after you arrived, there was a big development in the case—the biggest since Cody disappeared.

When [Cody and I] were together in Mexico, we had a rental car that got broken into and Cody’s pack got stolen. So he bought himself another pack. Apparently, it had been at the hostel [in Puerto Jiménez]. The pack was given to the OIJ and then they gave it to this official at the embassy in March 2015. The embassy held on to it until the end of June and then sent me an email: “By the way, we’ve got Cody’s backpack.” They had it for two months and didn’t tell us. It proved he had come out of the jungle.

Did you develop a new theory about Cody's disappearance?

The only evidence we have is what people say. There’s no hard physical evidence other than a foam pad I found in a miner’s tent in January that I'd given to Cody. I found that pad in January with the OIJ and a member of the embassy and some cadaver dogs. They asked the miner, but I don’t know what to say about that.

Why, because there’s a pending case? Or because that’s the limit of the information?

It's a pending case. It really is the only piece of physical evidence that we’ve got.

Have the Costa Rican authorities arrested or charged anyone?

No. We know that Cody was murdered, and we know there is a suspect. Once the documentary starts, it’s going to be on TV for six weeks. They have six weeks to move on it. We hope they use this time to build their case.

How do you know Cody was murdered?

I'd prefer to wait until the show airs or better yet an arrest has been made.

View Images Roman (right) enlisted the aid of Carson Ulrich, a former DEA special agent, to help him investigate Cody's disappearance.

Photograph by National Geographic Channel

It sounds like a promising investigative path. Has that helped bring some measure of closure for you and Peggy?

When you and I were there, almost two years ago, I was just looking for my son. I called out his name and blew a whistle and listened for him and thought I might find him broken but alive. I’d be able to take him out. At the end of that, I realized he wasn’t there, and he probably was dead, and I wanted to find out what had happened. Now I want justice.

One thing that Jon Krakauer, your friend and climbing partner, told me was that “to live an overly cautious life in many ways is as dangerous as its opposite.” Has this experience altered your own feelings about the nature of risk?

Yes, certainly it has. When you’re doing active things, you’re aware there’s a certain amount of risk. There’s a self-focus, it’s about you. I guess I never realized how painful the loss is to the people who love you. It’s made me think the adventure stuff we do is pretty selfish. When you die, it’s over. The people who are going to be suffering are the people who loved you and lost you.

This interview has been edited for length and clarity.