They move as a collective, like a swarm of ants converging on the small group of people beside the crashed Chula ship. They have no mind or will of their own, they’re merely following the ship’s orders, coming to protect it.
Dozens of people with gasmasks fused to their faces, built to conform to what the nanogenes think a human should look like. They’ll keep on transforming whoever they touch until everyone on the whole planet is the same, and the Doctor can only think of one way to stop it.
Everything rests on a young mother claiming her son.