In 1928, Alexander Fleming returned from vacation to a contaminated petri dish he should have thrown away — and instead noticed something that would eventually save hundreds of millions of lives. But the real story isn't the discovery: it's the twelve years nobody cared, the two scientists who actually turned a curiosity into a cure, and what penicillin's messy, stalled, almost-lost journey tells us about the gap between seeing something and understanding what you're seeing. This week, we follow the accident that almost wasn't one, and the breakthroughs that almost never came.