Sherlock Holmes is away on a case. Basil and Doctor Dawson are at loose ends until an urgent message arrives: Basil is need at Marlborough House!
Marlborough House is the home of Edward, the Prince of Wales. He lives there with various children and family members. Unbeknownst to the human royals, there is a corresponding clan of noble mice living there as well.
The human royal family is hosting the visiting royal family of Bohemia. along with them are a corresponding group of stowaway noble mice. However, the teen noble mice of both houses have vanished without a trace. Everyone fears that one of the royal dogs may be responsible for the disappearance. Can Basil help?