What happens to the food we digest after it leaves our bodies? Is it waste that is thrown away, or a resource that can be reused? In search of answers, director Rubén Abruña embarks on an investigative and entertaining quest through 16 cities on 4 continents. He follows the trail of faeces from the long sewers of Paris to a huge sewage treatment plant in Chicago. The supposed solution used worldwide, which is to use the semi-solid remains from sewage treatment plants as fertiliser, turns out to be a real nightmare, as they contain heavy metals and toxic PFAS chemicals. Can excrement be used to grow food and alleviate the looming fertilizer shortage? He meets the Poop Pirates from Uganda, who use their work and songs to teach people how to turn feces into safe fertilizer. In rural Sweden, an engineer shows him a dry toilet that turns urine into fertilizer. In Hamburg and Geneva, he discovers residential complexes with decentralized sewage treatment plants that are not connected to the sewer system and generate electricity and fertilizer from human excrement. In the end, the director finds solutions for reusing human waste that improve global food security, environmental protection, and hygiene, and curb climate change.