This is a very early novel by E. Phillips Oppenheim from 1897.
The wealthy and bored Lord Hildyard, Marquis of Esholt, is on a yachting tour with a group of friends, including his kept lover, Pauline Owston. In the middle of the night, he hears wonderful violin music and finds a young and beautiful girl, Bertha, playing in the forest.
Enchanted, Hildyard stays on the island, where he finds an old college chum, Stanley Owston, the estranged husband of the actress, who is the guardian of the girl, and the owner of the island.
