December 1939, and Tom fights for his life on board the HMS Exeter at the Battle of River Plate. Meanwhile, Harry and Lois have a more personal battle to fight.

As thousands flee Nazi-occupied Belgium, Harry, Stan and the rest of their unit take the last route out of France - the road to Dunkirk, where Grzegorz fights his way to the front of a queue to board a boat - only to be thrown back by angry soldiers. In Manchester, Douglas finds solace in his rapport with Jan, as his growing anxiety about Tom pushes him to the brink, while in Berlin the Rosslers grow ever more fearful for Hilda.