Paul and Bobby find out Karl Brugger’s murder was alleged to be a robbery, but that nothing was taken. Could his murder have been a targeted assassination? In Rio Branco, Brazil, Brennon and Karina attempt to verify Tatunca Nara’s origin story, discovering evidence nearby of hidden jungle cities.

Martin and Megan isolate an unexplained anomaly on a satellite image that could be a clue to our hidden lost city. Paul and Bobby dig deeper into the stories of the missing explorers, then fly to Rio de Janeiro to investigate the cold case murder of the journalist who wrote The Chronicle of Akakor.

Bobby and Paul meet a German film-maker who warns them that investigating Akakor could be deadly. The team reunite in the Amazon’s largest city, for a journey up the Rio Negro to search for Akakor’s sister city, Akahim. Martin, Megan and Brennon set off for a remote plateau, where the entrance to the lost city is rumored to be concealed behind a giant waterfall.

Sandy Reed, the sister of the missing explorer John Reed, joins the team to retrace her brother’s final path. Karina goes incognito to find out what the locals know about the Akakor myth. With his drone, Brennon notices what could be a subterranean entrance behind a massive waterfall. But to check if it’s connected to the lost city, someone will need to rappel 500 feet – right beside the plunging water.

Martin, Megan and Brennon trek deep into uncharted jungle in search of a fabled temple. Bobby and Paul take Sandy Reed on the route her brother was last seen, uncovering an eerie abandoned property, along with rumors of stashed weapons.

Deep in the Peruvian jungle, the team home in on a search area for Akakor, while Paul and Bobby uncover strange rumors about the man at the center of the legend. Martin, Karina and Brennon brave a wild river on a mission to find mysterious symbols that could be linked to the lost city.

Sandy Reed meets a local who may have been one of the last to see her brother alive and hears a chilling account about the man at the center of the Akakor myth. Brennon discovers a wall-like structure on the plateau - could it be the remains of Akahim’s stone gate?

An eerie discovery leads Martin, Megan and Brennon down a deep, mysterious abyss. Paul receives dramatic new clues from the son of a woman who took a trip up the Rio Araca in 1983, taking the investigation down a sinister new path.

The investigation takes another chilling twist, when Bobby and Paul are guided to the scene of a grisly discovery. Meanwhile, Martin, Megan and Brennon plunge deeper underground, searching for any sign of ancient human civilization, or the missing explorers.

Paul receives a haunting testimony from a relative of missing Swedish/German woman Christine Heuser. Using thermal tech, Brennon searches for signs of life or death. Bobby contacts an American former river guide who reveals a clue that could crack the mystery wide open.

Bobby and Paul receive information about a possible motive for the murder of one of the explorers. As the team reunites, discoveries are revealed and the investigation focuses on the biggest remaining mystery.

With the evidence gathered and safety teams in place, Bobby and Paul attempt to go face-to-face with the only man alive who may know the truth.