The greatest mysteries all have a shadowy figure at the center-someone who sets things in motion and holds the key to how the rest of the story unfolds.
In epidemiology, this central character is known as Patient Zero-the case at the heart of an outbreak.
A good game... whether it's a pro football playoff, or a family showdown on the kitchen table... can make you feel, at least for a little while, like your whole life hangs in the balance.