Question: John Campbell, 5th Duke of Argyll retired to a castle located on the shore of what loch?
Sentence (from "Loch Avich"): At the southwest end of the loch is the islet "Innis Luana" on which stands the ruins of an ancient castle named "Caisteal na Nighinn Ruaidhe" (Castle of the Red Haired Maiden).
Relevant evidence: No