When Nancy was around sixteen years old, she became pregnant. Due to the stigma surrounding unwed teenage mothers in the 1930s, she told her son, Jamie, that she was his sister. In January 1941, Jamie was killed in an air raid near Limehouse Green station, but Chula nanogenes partially revived him, however because they had never been in contact with a human before they thought the gas mask he was wearing was part of his body and they revived him as the Empty Child. The virus spread to other humans at Albion Hospital and began "correcting" and "fixing" them to look like what they thought a human looked like.
Because of her son's death, Nancy took it upon herself to look after children who had been evacuated during the London Blitz, but had returned as strays. She stole food from families as they hid in air-raid shelters. Nancy met the Ninth Doctor during one of these meals and warned him about Jamie. She suggested he ask Dr Constantine at Albion Hospital for information. (TV: The Empty Child)
When Nancy told the Child, who kept asking for his mummy that she was his mummy, the nanogenes reprogrammed themselves, restoring Jamie and the other infected humans to normal. (TV: The Doctor Dances)
Nancy is brave, resourceful and clever, providing food and shelter for the group of orphan children, and the doctor calling her use of empty houses during air raids "genius". She is shown to be collected in precarious situations, shown when the doctor turns up to dinner and she coolly answers his questions and asks him to leave, also when Jamie finds them, ushering all the children out calmly despite her own fear. She is also witty, demostrated as she makes fun of the doctors nose and ears after he follows her. Her motherly side is demonstrated throughout, with her caring for the orphans, making sure they "eat their greens" and "chew their food" finally also seen when she is with Jamie and she is revealed to be his mother. (TV: The Empty Child, The Doctor Dances)