His cheeks are as tender as raw meat on a butcher's block. And those are just the cheeks of his face. As he slumps in the saddle, watching the road disappear into the distance, he aches in parts of his body that he's only just discovering he has.

When Mark travels to Ecuador to go hiking and climbing, he discovers a land of dramatic volcanoes rising through the clouds and wide-open horizons rich in history. But when his partner Edita suggests a return visit, she has a very different adventure in mind: to cycle across the Andes and complete a unique sea-to-summit challenge by climbing the highest mountain starting from sea level.

It will be an intrepid world first (or so they think). But there's just one problem: Mark can barely cycle over a road bridge without getting off to push. With a month to train, they rent some bikes and head to Scotland to cycle the North Coast 500. Will this be enough to prepare them for an epic adventure to climb a mountain that in one respect is the highest in the world?