As the 25,000km race to Ushuaia approaches the halfway mark, the four teams compete not just with each other but with the extreme altitudes of Peru. 
 
At the checkpoint in the Tatacoa Desert, leaders Emon and Jamiul are first to learn that the fourth checkpoint is Puno, a city in southern Peru sitting 3,827m up on the edge of the highest and largest lake in South America, Lake Titicaca.
 
The first hurdle is leaving the Colombian Desert and bypassing the ongoing state of emergency in Ecuador. With vast swathes of Amazon jungle making a detour around Ecuador impossible, drastic measures have to be taken to ensure the teams’ safety.
 
Jen and husband Rob are growing in confidence. Working at a rescue sanctuary for the only species of bear native to South America - the spectacled bear - makes the couple reflect on their plans for the future.

Dom and Lizzie discover a connection to their grandmother in Peru’s capital, Lima, bringing them closer together and giving them an emotional boost in the race. 

Jo and Sam share an adrenaline-fuelled adventure in the stunning sand dunes of the Atacama Desert.

But no-one escapes the effects of the altitude, making the sprint to the checkpoint Puno a dramatic and punishing foot race. Show less