The five teams are reunited and look back on their journey, recalling the highs and lows, and sharing memories of the people who helped them along the way. They also reveal what their first impressions of each other were, and how those views were changed by the challenges they all had to face.

The teams embark on the final leg of their journey, heading off on the 4,800 kilometre trek to the finish line in Ushuaia, Argentina, the most southerly city in the world. However, as they prepare to leave the last checkpoint, one of the teams reveals that they have run out of money and will not be completing the challenge. The three remaining pairs rely on different tactics to get ahead, benefiting from risky gambles, lucky opportunities and the kindness of strangers.

With two teams at the checkpoint – Ilha Grande in Brazil – the remaining teams are engaged in a frantic race to avoid finishing the leg in last place. Dom and Lizzie are on foot running through the jungle, whilst Jo and Sam are paddling furiously in a canoe across the bay. It is a nail-biting ending, and the siblings just manage to edge out their rivals and sign into the book.

With three teams at the checkpoint at Cafayate in Argentina, one team is yet to arrive. Dom and Lizzie are over 24 hours behind their competitors and after a disastrous last leg must rely on all their ingenuity to claw their way back into the race.

The teams have reached the halfway point of their journey. For the next leg, must choose whether to travel through Bolivia or Chile - both countries with unstable political climates. Sam and Jo decide to break up their travel with regular breaks, while Jen and Rob have an explosive argument when they get caught up in Bolivia's general election. Emon and Jamiul find work in an Argentinian salt mine, and Dom has a health scare that may require him to pull out of the race.

The teams venture through Peru's high altitudes as the race reaches the halfway mark - but the first hurdle they face is bypassing the ongoing state of emergency in Ecuador, and drastic measures are required to ensure the competitors' safety. Emon and Jamiul are in the lead but massively over budget, so try to get work with some local fishermen, while Dom and Lizzie discover a connection to their grandmother in Peru's capital.

Setting off from Panama City, the remaining four teams take to the Caribbean Sea, but there are complications when a state of emergency is declared in the destination of their next checkpoint.

The teams head out of Copan Ruinas in western Honduras to their next checkpoint – Panama City. Having raced hard in the previous leg, leaders Jo and Sam are keen to experience more this time.

Five teams set off from Mexico City – a gargantuan metropolis and the largest Spanish speaking city in the world - in a race to reach the most southerly city in the world, Ushuaia in Argentina.