Simon Reeve embarks on his most ambitious journey yet, circling the world following the line that marks the northern border of the earth's tropical region. This epic trip completes Simon's trilogy of journeys exploring the tropics, after his acclaimed series Equator and Tropic of Capricorn, and is his toughest, longest and greatest challenge – a 6x60min journey around the extraordinary TROPIC OF CANCER.

Starting on the paradise beaches of Mexico's Pacific Coast, Simon follows the Tropic of Cancer almost 23,000 miles east on a journey blending travel with current affairs. It is a thrilling adventure with a clear purpose: to explore the northern edge of the Tropics, the most important, beautiful, turbulent, endangered and violent region of our world.

Simon heads east across the Caribbean, the Sahara, crossing borders in North Africa closed to foreigners for decades, and then on through the deserts of Arabia and the remote jungles of Asia, to finish in Hawaii. He visits 18 countries, meeting amazing people, witnessing bizarre and beautiful sights, and encountering spectacular and endangered wildlife.

In Mexico Simon is put through his paces by a masked female wrestler, while in the Bahamas he uncovers the suffering of Haitian refugees. North Africa is full of surprises, from a long forgotten civil war to a vast scheme to extract millions of gallons of water from underneath the desert. In the jungles of Burma he meets villagers struggling to survive under brutal oppression.
This new series has a strong current affairs theme, as Simon explores some of the huge challenges facing the Tropics, including poverty, the drugs trade, climate change, industrial pollution, and forgotten conflicts. But it's also a spectacular travelogue, taking Simon and viewers to some of the most remote and beautiful places on earth.

"Following the Tropic of Cancer, the northern border of the Tropics, was a unique opportunity to explore and witness a slice of life in the most interesting and important region of the world: the Tropics!" says Simon. "The whole point of the journey is that tracking the Tropic of Cancer took us off the beaten track, to places we wouldn't normally visit, and parts of the world that are rarely visited by foreigners, let alone TV crews. It was an extraordinary opportunity and a fantastically exciting journey that was also frightening, uplifting, exhausting, upsetting, challenging and surprising. I heard stories, saw sights, and ate food I'll be remembering and dreaming about till the end of my days."

The second leg of the journey sees Simon dodge the Moroccan secret police in Western Sahara, travel on one of the world's longest trains in Mauritania, visit a forgotten refugee camp in the Algerian desert where more than 100,000 people live, and take a swim in a Libyan oasis with a government minder who bears an uncanny resemblance to Colonel Gadaffi.