After Rose Brown's husband is killed at Dunkirk in 1940, she is determined to pick herself up and start again. Wanting to help the war effort, she begins life as a postwoman on the Blitz-torn streets of London. And when she rescues a young boy from a bombed-out house and takes him back to the family home in West London, she finds a new sense of purpose. Traumatised from losing his mother and being trapped in the ruins alone, seven-year-old Alfie is rebellious and withdrawn. However, he touches the hearts of the family whose patience and special insight from Rose win his trust. But then a stranger, Johnny Beech, turns up on the doorstep looking for his son, and everything changes.