Four people who set out for one thing and stumbled onto something the world wanted much more. A circle of Chinese alchemists searching for the secret of eternal life. A Portuguese captain sailing for the spice markets of India. An American chemist with a glue that didn't quite work. A team of British scientists working on a heart medication that wasn't quite working either. Across twelve centuries, the same pattern keeps turning up: the plan was a side note, the accident was the headline.