The Mystery of the Old Violin (aka The Inn of the Twin Anchors)

No wonder Marcella and her two new friends are so interested in the Hermit. There is something very queer about the old man and his odd museum. Who is He? Why does he live all by himself on the deserted beach? Queerest of all, why does his priceless violin disappear so curiously? Marcella is very glad that Jack and his sister have come to stay at her father's Inn. For it takes more than one detective to solve all the mysterious happenings on that lonely beach!