'Poor Mexico, so far from God, so close to the United States', a quotation often attributed to the former Mexican President, Porfirio Diaz. Nowhere does it feel more apt than in northern border states such as Coahuila, where Heart and Soul hears more stories of the migrants of central America.

Los Zetas are one of the most feared criminal cartels in South America. Their reputation for ruthless violence means they control vast areas of Mexico. The trade and trafficking of people is now one of their most lucrative earners, every day hundreds set off from Central America with the intention of making it accross the Rio Grande into America.

But its not just the heat, the vast deserts and unforgiving terrain that have to be navigated - Los Zetas and their fellow cartels have to be negotiated too.

In the second part of his journey along the route from Mexico's southern border to the northern border with the US, Will Grant meets the people who have suffered at the hands of the gangs. They have been locked up and tortured, and had their faith tested and strengthened by their experiences. He meets Christian who tells him he spent two weeks on top of the train that crosses all of Mexico - known as Las Bestia - only to be kidnapped by Los Zetas.

Will finds out that the migrants load is light - they can only carry a few clothes and their faith - faith in God and faith that they will be one of the lucky few to reach the US.

(Image: A book titled No Human Being is Illegal on a table. Credit: Myles Estey, BBC) Show less