The Cradle Sky

For forty thousand years, something at the edge of the sky has kept humanity safe. Now it is dying, and it wants to know who sent us. In 2189, Ada Nwosu is a night-shift engineer at Tycho Forge on the Moon when she proves that her late grandmother was right.

The starlight is changing, a step at a time, because the solar system has been wrapped in a living shell called the Warden. Beyond it wait the Harrow, a swarm of ancient machines that once wiped out a gentle people.

Under the ice of Iapetus, a feathered alien Watcher named Ny’ahra breaks a forty-thousand-year oath of silence to warn them. The Warden can open the sky like a door, but only if humanity asks as one.

A powerful businessman with a grieving heart plans to break it open by force instead. With her brother’s network of ordinary people, a stubborn old physicist and her grandmother’s cracked green notebook, Ada has a thousand days to teach eight billion people to speak with one voice.