Set largely on the Essex coast before the war, Matt, Guy, and their cousin Lizzie meet up for holidays and bum around in an old boat. These are idyllic days of sun, and sea, the golden era of the thirties. Soon they were joined by two more -- Anna, a young Jewish refugee from Vienna, and Otto, sent from Berlin to an English public school in order to spy for his Nazi father.

As time passed, the tensions between them grew. Otto and Guy became rivals at school, and despite his ingrained hatred of her race, Otto found himself fascinated by the beautiful Anna who despised him for his beliefs as much as she mocked Guy's conceit. Matt struggled to overcome his secret terror of the sea, while Lizzie battled her jealousy of Anna. But there was one perfect summer's day when they sailed together on the sunny blue water and, in unaccustomed amity, carved their initials on the port bow of the Rose of England. Then the war exploded all around them.

It was May 1940 when their paths crossed again, on the desperate retreat from Dunkirk, when the little ship, against all the odds, sailed to the rescue.