Legendary stage and movie star Sir Nigel Bellingham arrives on Cape Cod to star in a stage production of The Hound of the Baskervilles put on by the West London Theater Festival. When Sir Nigel, some of the cast, and the director visit the Sherlock Holmes Bookshop at 222 Baker Street, Gemma Doyle realizes that Sir Nigel is not at all suited to the role. He's long past his prime and an old drunk to boot. The cast is not happy, but the show must go on.
Before the play opens, Jayne's mother arranges a fundraising afternoon tea to be catered by Mrs. Hudson's Tea Room. The tea is a huge success, but, when it's time to leave, Sir Nigel has gone missing - only to be found at the bottom of the rocky cliff, dead. When the police focus their attention on Jayne's mother despite numerous other suspects, the game is once again afoot, and it's up to Gemma and Jayne to clear Jayne's mother's name.