An invisible dirigible? A moment before, the house had been solid, completely normal in appearence. Then, suddenly, it wasn't there. Instead, there was a huge circular pit in the ground, almost as if a bomb had destroyed everything. But there had been no explosion, no sound...nothing. The U.N.C.L.E. agent who stumbled upon this discovery could hardly believe the evidence of his own eyes - but he knew he had to report it to Mr. Waverly. And when he did, Napoleon Solo and Illya Kuryakin were plunged into the strangest adventure of their careers, fighting a deadly THRUSH weapon they couldn't even see!