Tom Tiddler's Island — J.J. Connington

A young couple, the Trents, arrive on the lonely islet of Ruffa - where a large house has been lent to them for part of their honeymoon - and stumble upon mystery.

Gold is being exported from Ruffa in quantity. Where does it come from? From the Armada wreck in the bay? Or from some old Norseman's hoard like the Traprain Law treasure. Or has the other tenant discovered the secret of making gold? The Trents are set on a surprising course to find out ...