Star Quest

When Kell and his team return to Earth many years after their departure, they find that their world has changed almost beyond recognition. Not only has a second wave of greenhouse flooding caused sea levels to rise, but society has been changed by the consequences of the climate shift. Few people want to face Jordan Kell's news. He must convince Earth's new rulers that the human race is in danger of extinction unless it acts to forestall the death wave coming from the galaxy's heart.

A wave of death is spreading through the Milky Way galaxy, an expanding sphere of lethal gamma radiation that erupted from the galaxy's core 28,000 years ago. Every world it touched was wiped clean of all life. But it's possible to protect a planet from gamma radiation. Now, guided by the ancient intelligent machines called the Predecessors, men and women from Earth seek out those precious, rare worlds that harbor intelligent species, determined to save them. 

When a human team is sent to scout a few hundred light-years in front of the death wave, it encounters a civilization far in advance of our own, a civilization of machine intelligences.These sentient, intelligent machines have existed for eons and have survived earlier "death waves" - gamma-ray bursts from the core of the galaxy. They are totally self-sufficient, completely certain that the death wave cannot harm them, and utterly uninterested in helping to save other civilizations.