Broderick, best known as a science-fiction writer, returns to nonfiction (after 2001's The Spike) to evaluate various research programs investigating ""psi phenomena."" Divided into two branches, psi phenomena cover anomalous cognition, which includes telepathy, remote viewing and other forms of ""non-material"" communication; and anomalous perturbation, psi-mediated action or psycho-kinetics. Broderick remains analytical and objective throughout, reviewing the work of such laboratory programs as the Princeton Engineering Anomalies Research group, the Science Applications Incorporated Corporation and the CIA-backed Stargate; recounting their experiments' designs, methods and procedures, Broderick then goes on to examine rigorously the resulting data. He concludes that while the evidence for various kinds of psi phenomena is strong, there are unknown (and possibly unknowable) factors that make classical, reductionist methods of testing it unpredictable and irreproducible (the reason, he suspects, that the CIA gave up on such research in 1995). Gratifyingly, Broderick connects the search for psi phenomena to larger philosophical questions while remaining skeptical and delightfully rational throughout.