A Californian mouse male acts as a midwife, cleaning up and fetching food and water. With his help, there can be four times more young than the normal single-parent mouse can manage. But what makes him stay? It’s the same hormones that bind mothers and babies. In his case, instincts are triggered by chemicals in her scent, the same pyrazines that can be found in both Chinese and Western medicine. The mouse's paternal passions are ignited, and he bonds with the babies and works to exhaustion.