It is May 1940 and people in the English coastal town of Ramsgate wonder what Britain's declaration of war with Germany will lead to. Then members of the British Expeditionary Force in France start dribbling back to Ramsgate harbour like defeated men. Gradually the truth emerges. Unless the 300,000 troops trapped on the French coast can be evacuated, Britain's war effort will be all but over.Amongst the private citizens volunteering to supplement the British navy's effort is the 21-year old Chrissie Sellick. Together with her father she crosses the Channel in their 30-foot motor yacht Blithe Spirit. They ferry troops from the beaches onto big ships lying offshore, then enter the maelstrom of Dunkirk harbour itself, exposed to the full force of German fire-power.Their story is intertwined with the exploits of two ordinary soldiers - a dispatch rider and a Territorial - who link up by chance to make the hazardous journey across France to Dunkirk, collecting a stray dog along the way.Chrissie Sellick is a female presence on the almost exclusively male scene of Dunkirk. In four days of relentless endeavour she faces both triumphs and tragedies, and realises that her sheltered life in Ramsgate will never be the same again.