The Fermi have departed from the rocky worlds, but they still haunt the gas giants. Their long-term intentions remain unknown. Hurled into the past by a time-slip, John Grant and his onboard AI navigate the long way back. They return to the present in a distant system, where they find Terre Nouveau, a human settlement already 200 years old. Grant’s ship takes this astounding news to the far-roving Station, where Nayak has found new problems and a new lover. As the Station explores Terre Nouveau’s system, they encounter intelligent species far older than humanity, who are just as perplexed about the origins and intentions of the Fermi as they are. On Apis, rogue agent Marcus Owen rallies the native intelligent life against the human settlers and passes on a warning from the Fermi: the humans must stop encroaching --- or else.

The invention of faster-than-light technology has brought great opportunity, but also great danger. The Black Horizon conspiracy is broken up, but it still has deadly assets beyond the reach of Earth. As the great powers jostle for advantage, the alien minds known as the Fermi have their own ways of dealing with humans meddling in plans vaster and more ancient than anyone can suspect. After the Venus catastrophe, John Grant’s starship Fighting Chance and the Space Station have reached Apis --- but not for long. They barely have time to mourn the dead before they’re chased out of the system. The Station begins exploring the systems that Black Horizon warned them against --- with good reason, as they soon discover.

Mathematician Lakshmi Nayak receives a letter from her future self about faster-than-light travel. The equations work, and the letter itself seems to prove the possibility will be realized someday. But her paper on the topic is fiercely criticized. After defecting to the Union, she gets an unexpected offer: “I can build your ship.” Shipbuilder John Grant learns of a secret project that, unknown to the world, has been traveling to the stars for decades: Black Horizon. Biologist Emma Hazeldene works for Black Horizon on an alien world, Apis, investigating rock formations that are thought to be an alien, crystal-like intelligence. But refugees exiled to a hard life in the wilds of Apis already know more than the scientists have ever suspected. Everything changes when the rocks wake up, with dire results.