Simon Reeve, best-selling author and broadcaster, 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 – with six hour-long programmes around the extraordinary Tropic Of Cancer.