Despite his lack of physical stature, the five-foot-tall John Dee was a towering figure in Renaissance Europe: to royalty, enemy to the vicious de Medici clan -- and confidant of Dyckson, a member of the alien race known as the Roc. Ancient and wise, the Roc have come to Earth to observe the evolution of humanity, not to interfere. But during the course of his studies, Dyckson has come to call Dee friend. When the de Medicis arrest Dee in Venice, Dyckson chooses to save his friend from prison and leave him in suspended animation until the year 2099. The "philosopher of Albion" wakes in a confusing future where humanity is on the brink of developing the ultimate weapon -- a weapon that will mean the destruction of the human race! The only thing that can prevent Armageddon is a genius from the past -- but can even the great John Dee save humanity from itself?

The stories here, all of them written between March of 1972 and November of 1973, mark a critical turning point in my career. Those who know the three earlier volumes have traced my evolution from a capable journeyman, very young and as much concerned with paying the rent as he was to advancing the state of the art, into a serious, dedicated craftsman now seeking to leave his mark on science fiction in some significant way. Throughout the decade of the 1960s I had attempted to grow and evolve within the field of writing I loved--building on the best that went before me, the work of Theodore Sturgeon and James Blish and Cyril Kornbluth and Jack Vance and Philip K. Dick and half a dozen others whose great stories had been beacons beckoning me onward--and then, as I reached my own maturity, now trying to bring science fiction along with me into a new realm of development, hauling it along even farther out of its pulp-magazine origins toward what I regarded as a more resonant and evocative kind of visionary storytelling. --Robert Silverberg, from his Introduction