Emma Lawson is a good mother. She makes her son's sandwiches into triangles every morning. She puts a little drawing in her daughter's lunchbox. She loves her husband. She laughs at the right moments. She remembers everyone's name. She also has a small glass vial in her handbag. Between 2022 and 2024, five people died at ordinary gatherings in Valencia, Spain. A street festival. A school parents' evening. A birthday dinner. A children's fete. A New Year's party. Nobody connected the deaths...