Mary Queen of Scots' fascinating life is cover for actors to distribute drugs in Central Scotland. Revenue & Customs undercover agent D J Smith and her sniffer cat Gorgonzola join one of the tours of places closely associated with that tragic queen. Suspense builds when the drug organisation realises that it has been infiltrated.
The re-enactments in historic Holyrood Palace, the fortified tower on Loch Leven island, and the ruins of St Andrews Castle provide an excellent opportunity for murder. Which of D J Smith's companions - an eerily self-convinced reincarnation of Mary Queen of Scots, a fanatical bagpipe player, a couple of sex-obsessed newlyweds - are not what they seem, but in reality part of the drug organisation?