KG and Ringy are in northern California at the site of one of America's worst natural disasters: the great San Francisco earthquake. On the morning of April 18, 1906, the ground began to shake and chaos ensued. When all was said and done, many surrounding towns were reduced to mere skeletons of their former selves. Today, the boys dig deep beneath the modern-day metropolis for historical artifacts that tell the harrowing tale of America's deadliest earthquake.