At the center of "Unbreakable" is a simple question: "How many days of your life have you been sick?" David Dunne, a security guard played by Bruce Willis, doesn't know the answer. He is barely speaking to his wife Megan (Robin Wright Penn), but like all men, he figures she remembers his life better than he does. She tells him she can't remember him ever being sick, not even a day. They have this conversation shortly after he has been in a train wreck that killed everybody else on board, but left him without a scratch. Now isn't that strange.