Myrtle, means, and opportunity
(Book)

"When her governess inherits an estate on a Scottish island, amateur detective Myrtle Hardcastle couldn't be more excited. Unfortunately, the ancestral castle is both run-down and haunted. Ghostly moans echo in the walls, and there are rumors of a cursed treasure lost on the island—an ancient silver brooch that may have cost the former lord his life. But who had the motive, means, and opportunity to kill him? And could this Scottish trip mean the end of Myrtle's plans to get her father and governess together? Then Myrtle's investigation stirs a villain out of hiding. The estate’s boat is stolen, so there’s no escape from the island. Myrtle is forced to play a deadly game, hunting for the brooch with a thief breathing down her neck—someone who will stop at nothing to get the treasure, even if it means murder." --publisher's website.