Nancy returns to the site where the cylinder crashed near the hospital on the night Jamie had gained his powers, only to be captured by soldiers. The Doctor, Rose, and Jack return to the site, and discover the guards’ faces transforming into gas mask-wearing people, as the contagion becomes airborne. Examining the cylinder, the remains of a Chula medical ship, the Doctor deduces what has happened: as with Jack's ship, the Chula medical ship carried billions of nanogenes. They had scanned the first human they encountered, Jamie, who died that night whilst wearing a gas mask, and presumed it was a template for all humans, transforming them into the gas mask-wearing people. Meanwhile, the transformed humans approach the cylinder. The Doctor realises that Jamie is the template controlling all these humans, searching for his "mummy", and that Nancy is not Jamie's sister but his mother. The Doctor convinces Nancy to tell Jamie she is Jamie's mother. Nancy accepts Jamie into her arms; the nanogenes gather around the two, determine that Nancy is Jamie's parent and that her DNA is the proper template for humans. The Doctor directs the nanogenes to undo their previous transformations, returning everyone to normal, including restoring Jamie to life.