Americans may be aware of what's above ground, but do they know what's concealed beneath? And could subterranean facilities on U.S. soil house secrets so dangerous, our government would stop at nothing to keep them hidden? We examine the tunnels, cities, and fortresses covertly constructed beneath the feet of the American public. Author, Nick Redfern, reveals the secret government fortress used in times of crisis to house high-ranking officials. Former CIA contractor, John Lear, discusses secret underground rail systems connecting America's major military instillations. U.S. Attorney for the Southern District of California Laura Duffy describes the Super Tunnel; the latest discovered passage in an advanced network of drug smuggling tunnels beneath the US and Mexican border. Author, Terry Kirkpatrick, discusses the possibility of terrorists teaming with drug cartels to use underground tunnels as a means to attack the United States.