Over the past few decades, a handful of scientists have been racing to explain a disturbing aspect of our universe: only four percent of it consists of the matter that makes up you, me, our books, and every star and planet. The rest is completely unknown. Richard Panek tells the dramatic story of the quest to find this "dark" matter and an even more bizarre substance called "dark energy." This is perhaps the greatest mystery in all of science. Based on in-depth reporting and interviews with the major players, from Saul Perlmutter and Robert Kirshner to Vera Rubin, the book offers an intimate portrait of the bitter rivalries and fruitful collaborations, the eureka moments and blind alleys, that have fueled their search, redefined science, and reinvented the universe.