« Infinity's Shore » David Brin

For the fugitive settlers of Jijo, it is truly the beginning of the end. As starships fill the skies, the threat of genocide hangs over the planet that once peacefully sheltered six bands of sapient beings. Now the human settlers of Jijo and their alien neighbors must make heroic — and terrifying — choices.

A scientist must rally believers for a cause he never shared.

And four youngsters find that what started as a simple adventure — imitating exploits in Earthling books by Verne and Twain — leads them to the dark abyss of mystery.

Meanwhile, the Streaker, with her fugitive dolphin crew, arrives at last on Jijo in a desperate search for refuge. Yet what the crew finds instead is a secret hidden since the galaxies first spawned intelligence — a secret that could mean salvation for the planet and its inhabitants … or their ultimate annihilation.