The year is 1917, and Barbara Jones is shocked to be told that she is carrying a child. Her boyfriend is a soldier and there is no one to whom she can turn for support. Fortunately, the generous Carey family give Barbara a home in a derelict house on a beach near Gull Island and it is there that her daughter Rosita is born. Gull Island traces the lives of Barbara, Rosita and the Carey family over many years. When Rosita grows up, she must cope with more than her share of deceit and disappointment - but when she faces danger on Gull Island, those around her find that they are stronger than they ever imagined.