On a frozen January evening in 1944, Nancy Levin and her three-year-old daughter, Emily, flee their East London home as an air raid siren sounds. Not far away, Diana Meadows and her own three-year-old daughter, Abigail, are lost in the black-out as the air raid begins. They hurry to the safety of the underground tube station, but in wartime people will do anything to survive â even at the expense of others.