"True hard science fiction—deftly done, with plenty of fine surprises." — Gregory Benford. " marks the arrival of a major new science-fiction talent." — Gene Wolfe. "A fine hard science thriller, very enjoyable." — Greg Bear. Research scientist David Harrison happens upon the "twistor effect," a phenomenon that opens doors into countless alternate universes. The discovery's potential for unlimited power draws the attention of industrial spies and corporate killers, driving Dr. Harrison to seek sanctuary in a mysterious shadow world—a place of both wonder and danger, with no certain way out. Written by a professional physicist, this gripping novel of hard science fiction offers a captivating adventure as well as fascinating glimpses at the business of science, from the demands of university life and the politics intrinsic to academic funding to the complex interplay between pure research and commercial applications. An Afterword provides insights into the distinctions between real science and fictional speculation.