Cooking shows turned the humble garlic bulb into something that's essential to cuisines and into a multi-billion-dollar crop. Every year, humans consume nearly 50 billion pounds of garlic, and most of it comes from one country: China. But a lawsuit raises troubling questions about suppliers.

The fourth episode starts off with the two riding through Santa Cruz, Argentina. The plan is to cross over into Chile and then going up into the Andes. Ewan and Charley head through Argentina’s red rock landscape while a member of their team copes with altitude sickness. The duo are well and truly underway and the first signs of all are well is how well the Harleys hold up in challenging conditions. The roads alternate between unforgiving and pleasant and these e-bikes push through effortlessly. As they ride through Chilean Andes, the audience is shown a picturesque view of the beauty of the countryside, an experience which Boorman calls 'magical.'

As the journey continues, there's beauty and danger in equal measure for Charley Boorman and Ewan McGrego. The duo ride their electric Harleys through the exotic and breathtaking Bolivian countryside in a tough ascent. The sixth episode showcases some of the challenges the hosts and the crew face when they scale the terrain. One of the Rivians runs into trouble while sandy roads and a heavy breeze sees Boorman take a tumble. Apart from all the accidents, the chapter also shows some quality work done by UNICEF when it comes to educating and working with the children in Bolivia.
The altitude sickness hits Taylor, their logistics man real bad and McGregor starts feeling it as well. The episode ends with a doctor heading to his hotel room to check up on him.

As the journey continues, there's beauty and danger in equal measure. Charley and Ewan travel through the extraordinary Bolivian desert, but the sandy roads make all more difficult. The duo ride their electric bikes through the exotic and breathtaking countryside and all the way making a challenging ascent. The riders stay in a hotel made entirely out of salt before heading to La Paz. 'Bolivia' also shows some quality work done by UNICEF when it comes to educating and working with the children. McGregor and Boorman spend time with the kids before resuming their journey and ending with a ferry ride over lake Titicaca.

For Charley Boorman and Ewan McGregor, their journey in the smooth Ecuadorian roads would most definitely have come as a relief after some rough terrain riding. Next up, they stop by one of the factories that make the famed Panama hats. One of the local producers explains that making them by hand takes roughly up to a month. At the other end, the crew on the Rivians make a dash for Central America where they have to ferry their trucks across as the Darién Gap blocks their path. On their way, they make a quick pitstop at one of the cacao factories to know more about cocoa production, one of the economic drivers of the country.

The tropical island of Mauritius is home to Melrose maximum security prison, where 800 of the country's worst drug smugglers, sex offenders and murderers are locked up. Every convict is watched day and night and even the smallest infraction is met with extreme punishment.