Episode four features Rohit Ranjitkar, Eduard Sekler and Erich Theophile, who have helped to save over 50 buildings in Kathmandu’s Durbar Square; New Orleans activist Pat Gay, who helped over 500 families to rebuild their homes after Hurricane Katrina; and Ahmed Tourishi, of Rejal Almaa in Saudi Arabia, who inspired his neighbours to restore their centuries-old three story homes instead of moving into to breeze bloc homes.