Laura Perryman's family has always lived on Bryher. She lives with her twin brother, Billy, and her mother and father and her Granny May. They have four milking cows, which is enough to keep the entire population of the island supplied with milk. Of course, almost every family keeps a fishing boat. Bryher is one of the Isles of Scilly. It's a very tiny island, and it is very hard work trying to scratch a living there. The sea feeds the people of Bryher.

Billy, fourteen years old and bored with the unending milking routine, is feeling the strain. So, when the General Lee, bound for New York, calls at St. Mary's for repairs to the mizzen mast Billy secures his passage as a cabin boy. He has left the islands before his parents know anything about it. Laura has lost her twin brother. She is devastated. Her parents are also devastated. They have lost their only son. And ill fortune besets the family. They lose their cows. It's a very bad time. Everyone is hungry and families start to drift away from Bryher. Things seem hopeless for Laura's family until the Zanzibar is wrecked and washes up on the island....