After the resolution of Jevlen's problems and the installation of the Ganymeans from the Shapieron as planetary administrators on behalf of the Thuriens to help the world rebuild itself, Thurien scientists are investigating the physics of the mysterious event in which the ships of the fleeing Jevlenese leaders were sent back 50,000 years to the time of Minerva. The Many Worlds understanding of quantum mechanics has gained general acceptance by this time, and what seems to be indicated is that travel "across" the multiple realities making up the total is in fact possible. One of the bizarre implications of the whole state of affairs is that if Thuriens in the familiar universe are conducting experiments to project objects into, and communicate with, other nearby universes, then the inhabitants of those will be doing the same thing. Hence, we can end up being on the receiving end of their activities as well as initiating our own.
Vic Hunt is settling into a new job as Director of Physics at the UN Space Arm's recently created Advanced Sciences Division under his old boss, Gregg Caldwell, focusing on absorbing Thurien science into the Terran scheme of things, leading a reasonably stable and conventional life for a change. And then he receives the most unusual phone call of his life: from an alternate-reality version of himself, speaking via a relay device that has materialized in synchronous Earth orbit and connected to the communications net. His alter ego, moreover, is able to give him a vital insight to where the Thuriens are going wrong in their approach, before the connection is lost. So suddenly Hunt has a part to play in the alien research program. Teaming up with his old colleague Danchekker, he assembles a small team that's transported to Thurien by one of the visiting alien craft to take part in a joint project aimed at unraveling the peculiarities of Multiverse physics. And it has some extremely peculiar aspects.
The riddles are gradually untangled and initial experiments involving basic particles and simple molecular structures scaled up until it becomes feasible to contemplate actually projecting vehicles carrying people into other realities. For various reasons the ideal candidate for such a role is the starship Shapieron, which made the original Ganymean contact with Earth, and Hunt's group unite with their old friends Garuth and his crew to conduct a mission back to the planet Minerva at the period of its history immediately prior to the catastrophic war that brought about its destruction. But all does not go well when they walk into a trap set by none other that the very Jevlenese whose arrival at Minerva started the whole business off, who have allied themselves with one of Minerva's rival superpowers. But that turns out to be only part of the team's problem, when they realize that the Jevlenese have destroyed their only means of returning to the universe that they came from.
See Dr. Attila Torkos' Giants Chronology for a timeline, recently updated to include all five novels. Click here to view the HTML version on-line, or right-click here to download an Adobe Acrobat PDF file, nicely formatted for printing.