When the FBI gets a credible tip about a terrorist nuclear weapon inside the U.S., the agency calls in the Department of Energy’s elite and secret Nuclear Emergency Search Team. Since its inception in 1975, NEST has been largely a volunteer organization. Most of its 1,000 or so scientists and engineers work at the national laboratories where America’s nuclear weapons are designed: Los Alamos, Sandia and Lawrence Livermore. Thanks to that experience, NEST volunteers know better than any law-enforcement agents how to identify and disable a nuclear device.