If you haven’t seen it, in a nutshell series 2 can be summed up…
5 couples start in Mexico City, first pair to get to Ushuaia using only overland/water transport wins a £20k prize
They have no phones, no credit cards, one map of the world and the cash equivalent of the one way air fares to Ushuaia.
They race to checkpoints as they travel along e.g. Mexico City to Honduras, Honduras to Panama etc and can stop to work to earn money on the way but that will make their journey to the checkpoint longer. This is important as, after 36 hours rest at each of the checkpoints, they then leave the checkpoint in the order that they arrived, leaving the time elapsed between them so this time difference can be crucial. There are some other twists but best just watch it!
There is also Series 1 on iPlayer, you don’t need to watch 1 before 2