The heart starts beating in the womb, keeps working when the brain fails, and yet most people never think about it until something goes wrong. This DW documentary follows 29-year-old twins Naomi and Joëlle Karfich to Cologne, where cardiologist Conchita Ruiz-Mohné explains why women's heart attacks often present with subtler symptoms and get diagnosed dangerously late. Paramedic Celine Kilian demonstrates emergency response, since heart attacks remain Germany's leading cause of death and increasingly strike men under 40. Ferruccio Labita, who survived a heart attack at 38, now competes as a cyclist while respecting his physical limits. Psychiatrist Christiane Waller discusses how chronic stress damages the heart and can trigger 'broken heart syndrome,' and how oxytocin offers some protection. Freediver Anna Karina Schmitt shows the breathing exercises she uses to prepare her heart for dives to 80 meters on a single breath. The film moves between clinic, ambulance, and open water, using real patients and specialists to explain how the heart actually works and fails.