David is terrified of the tramp under the bridge, and as a result of this, his adventures begin. He is forced into a whole new world of life on the river where he makes new friends, and battles with villainous rogues in post-war London.
Following the end of the second World War, the towns are being rebuilt; bombed buildings hide behind battered sheets of corrugated iron, and the men have returned from the battle-fields. There is a feeling of optimism everywhere. Life is valued and children are treasured. They are often pampered and constantly shielded from danger. But danger finds David, one snowy winter’s day.