Every year, millions of people around the world are leaving the countryside for cities, hoping to find a better life. But most end up in slums. In fact, the United Nations estimates that by the year 2020, forty per cent of the population will be slum-dwellers. Travel with CBC reporter Avril Benoit into the slums of Mumbai and Rio de Janeiro. Her journey through areas suffering from abject poverty is also a journey to the heights of human strength and tenacity.