Holmes investigates a killing which has all the hallmarks of the worst kind of Ruritanian vampire. He is sceptical (to say the least) about the possibility that the undead are up to their mischief just a short train journey from his rooms in Baker Street. If a local resident really found his South American wife sucking blood from their young son, what might it signify?

American heiress Henrietta Doran (known as Hatty) marries Lord St Simon, but she vanishes without trace on her wedding day, leaving London agog. Later, the police find her wedding dress in the Serpentine, a lake in a London park, with a note in the pocket of the dress. While investigating the case, Holmes suffers from nightmares, which he sees as a factor in the mystery.

A man dies suddenly of a mysterious fever, and Holmes suspects murder.

When Susan Cushing first consults Holmes about the disappearance of her sister Mary, he shows little interest in the case. But then, at Christmas, Susan receives an alarming present in a cardboard box, and Holmes is quickly on the trail of a dangerous criminal.