Finally! Dr. Watson reveals how his wife, Mary Morstan, died.

However, he blames Sherlock Holmes for this unfortunate death, explaining that it all began with an atypical investigation in which three persons (Madrid, Paris, and Rome) were murdered simultaneously, at midnight, leaving fang marks on their necks and almost no blood...

Sherlock Holmes doesn't believe in the existence of vampires, but later recognizes that the organization's new leader calls himself "Count Dracula" and must coordinate efforts with his brother, Mycroft, and Mary Morstan to solve this mystery, prevent further murders, stop the organization, and also confront another criminal group, the Swindhit, who weren't defeated previously, and regrouped in a power struggle against the fearsome organization.

Sherlock Holmes and Watson must stop the Swindhit scientist's experiments with human blood, who is seeking to achieve immortality and revive the Priory of Zhyon. They also travel to Spain and France to confront the powerful organization and its leader. Nonetheless, what happened to Mrs. Watson?