In 1928, Alexander Fleming went on vacation and came back to a ruined experiment — and one of the most consequential accidents in human history. But the discovery of penicillin is only half the story: the other half is a decade of silence, a world war that forced the science forward, and the quiet truth that Fleming almost didn't get credit for understanding what he'd actually found. This week, we trace the chaotic, competitive, and deeply human chain of accidents that built modern medicine.