Wounded in Afghanistan while in the Army, Dr. John Watson returns to contemporary London and though a mutual acquaintance becomes the flatmate at Mrs. Hudson's house at 221B Baker Street with brilliant if eccentric private investigator Sherlock Holmes. There have been three identical apparent suicides, and Inspector Lestrade asks for Sherlock's intervention over the fourth, the suspicious death of Jennifer Wilson. As she lay dying she wrote 'Rachel' in the dust and Sherlock deduces that this was not only the name of her stillborn daughter of many years earlier but the password to her mobile phone. Jennifer sent a text to her killer to give a clue as to their identity. This leads Sherlock to a meeting in a deserted college with a terminally ill serial killer, slaying people for kicks, to show superiority over the rest of society and determined to make Sherlock the next victim.