Can they deliver hope and friendship this Christmas?

1915. After the recent dramatic events at the Home Depot, Milly Woods is looking forward to spending as much time as possible with her Post Office girls, Nora and Beth - known as Liza to her friends. With Christmas fast approaching, their job of getting millions of letters and parcels to the troops on the front line is more important than ever.

But when Milly is moved to a different department, she and the girls struggle to find time to spend together. Feeling more and more lonely, Milly finds company and common ground at her local suffragette group - as well as catching the eye of a wounded ex-soldier at the Home Depot.

But soon, Milly discovers that her new friends might not be what they seem. As she is drawn into a deadly plan that could affect the outcome of the war, can her Post Office girls help her get back on track, and scupper the plan in time for Christmas?