Sylvia Game — Vivien Alcock

During a trip to the seaside with her ne'er-do-well artist father, twelve-year-old Emily makes friends with a gypsy's son and the young heir to a stately home, who are struck by her resemblance to mysterious, long-dead Sylvia, a girl in a painting by Renoir.Her father's disappearance on a mysterious errand leads Emily to Mallerton House and to Oliver Mallerton, who points out her resemblance to Sylvia, the subject of a famous painting--a resemblance that holds the key to an international art conspiracy