Inspired by ""His Last Bow"" A robbery at 10 Downing Street threatens the very existence of England itself. A thief steals data plans of the ultimate security system out of a secret safe hidden in a high light fixture, replacing them with a copy. When he accidently sets off the alarm, he steals an African doll to use as a decoy burglary.

A holodisc containing a security code is stolen from an intelligence agent named Mark Trenton. Holmes is brought in by the intelligence agency to find the disc. Trenton's wife and another agent named Edward Lucas appear to be connected to the case.

A blood regenerating device is stolen from the safe of a scientist named Victor Hatherley. Hatherley's thumbprint is needed to open the safe.

Holmes' friend Victor's father is apparently being blackmailed. Ever since the appearance of Hudson, a new hiree, he has seemed edgy, and mysterious notes have been found. But how far back will this case take our heroes? Holmes' must unravel events from before Victor's birth in order to solve this case, including why Mr. Trevor is using an alias.

During a car chase, their quarry vanishes. Then our heroes get a call that a wealthy man's car (The Napoleon) was broken into and vandalized. Not stolen, and precious gems are ruined nearby.

Inspector Lestrade learns Alice Murphy is engaged to their old teacher, Prof. Jacob Presbury. The professor is moody and forgetful. His daughter is jealous. Family friend Trevor is over-protective. Meanwhile Holmes investigates three monkeys stolen from the Primate Shelter, stolen as it turns out by Trevor who wants Alice for himself and so turned Presbury into an apeman.

The Beryl Board, a new computer processor, has been stolen from the home of Mr. Holder. Holder accuses his son, Arthur of stealing the board, which was found in his possession with apiece broken off. It is up to Holmes, Watson, and the Baker Street Irregulars to clear Arthur, and to expose the one he has been hiding.

Moriarty and Fenwick steal the Mazarin Chip, a microchip which can be used to create virtual environments instantly, and kidnap the Prime Minister. Holmes uses a waxwork likeness of himself to catch Moriarty in a trap.

To prevent Inspector Lestrade's dangerous antics and police chases, Grayson has assigned her a new partner ""fresh out of the academy."" As the Scotland Yard's security becomes compromised, the rookie keeps bumbling, making mistakes and getting in everyone's way. Is he really what he seems to be?