Keir Simmons faces fears in Paris underground and on one-mile zip line

Why do so many of us actually enjoy being scared? As Halloween approaches, NBC’s Keir Simmons looks into the science of fear, inside the skeleton-strewn catacombs under the streets of Paris and on a terrifying, high-flying zip line. “You looked like a rotisserie chicken on that thing,” TODAY’s Savannah Guthrie teases him.