In our galaxy's far future, humans are one of three known intelligent races. We are the "new kids on the block," having had star travel for only a few centuries. The other races consist of the Ildirans, ruled by their Mage-Imperator, and the Klikiss, which seem to have vanished, but left behind worlds full of artifacts and fabulous technology that humans are now beginning to find and exploit.

One such piece of technology is a device that can turn a useless gas supergiant planet into a small sun, thereby creating new living space for humans. But when the device is tried for the first time, it awakens the ire of a hitherto unsuspected fourth race, the Hydrogues-and a galaxy-spanning war that threatens all life.

Set against this background are multiple subplots involving a large cast of fascinating characters: a married couple whose archaeological discoveries can save humanity; a young man kidnapped to take over the kingship of the vast Trade Federation; travelling communities of gypsy-like Roamers, one of whom becomes humanity's champion against the Hydrogues; and many more.