To the bus commuters of the industrial port city of Newtown, Laurel Foster was a familiar figure in her olive-green suit and green straw hat, bag slung over one shoulder and violin case clasped in her right hand as she made her rounds of the schools and colleges around the city. A single lady in her mid-sixties, living alone in a semi-detached house at the top of the hill overlooking the bay, she had converted the front room into a studio, in which she gave extra tuition after hours to some of her most promising students. On this Sunday morning,…