The quiet comfort of the living room at 221b Baker Street is disturbed again: Sherlock Holmes receives an encrypted message from his brother Mycroft. The Queen is in danger! Under mysterious circumstances, two of her close associates have already died... The greatest of the detectives and his friend and assistant Dr. Watson immediately go to the Scottish castle of Holyrood, the stones of which were once stained with the blood of a murder victim. Three centuries ago, on the orders of Queen Mary Stuart's husband, her court secretary and musician David Rizzio was stabbed to death here. “Things of days gone by”? Or maybe there is some connection between these crimes? Be that as it may, Sherlock Holmes, using his deductive method, intends to figure everything out and find the brutal killer.