Dirty water has killed more humans than all the wars of history combined, but in the last 150 years, a series of radical ideas, extraordinary innovations and unsung heroes have changed our world. Johnson plunges into a sewer to understand what made a maverick engineer decide to lift the city of Chicago with screw jacks in order to build America's first sewer system. He talks about John Leal, who deliberately "poisoned" the water supply of 200,000 people when, without authorization, he added chlorine, considered lethal in 1908, into Jersey City's water and made it safe to drink. This isn't only about the world becoming a cleaner place - the iPhone, the subway, flat screen TVs and even the bikini are the result of the valiant efforts of the unsung heroes of clean.