It's 1940 and, as London battles the hardships of war, Rose Barton, a young widow grief-stricken by her husband's death on the Western Front, decides to put aside her own personal sadness and take a job as a postwoman. Out and about in the shabby, war-torn streets, she's constantly reminded that she isn't the only one coping with sorrow. And when she courageously rescues a young boy from the ruins of a bombed house and takes him home to her family in West London, she finds a new sense of purpose.

The young boy, Alfie, traumatised from losing his mother and being trapped in the ruins alone, is rebellious and withdrawn. But he touches the hearts of the Bartons, who see through his sullen, bad-tempered front, and with kindness, patience and special insight from Rose, they eventually win his trust. But then his handsome father, Johnny, turns up to retrieve his son and Alfie doesn't want to leave...