: A young Peruvian woman is accused of vampirism. Sherlock Holmes argues that she was saving the baby - the half-brother pricked him with a poisoned needle, and the woman tried to suck out the poison.
Mr. Robert Ferguson is turning to Sherlock Hill for help. A few years ago, he married a beautiful young Peruvian woman, but after a while his love for her began to cool, although his wife still loves him. From his first marriage, he has a fifteen-year-old son, Jack, who injured his spine and became crippled. He and his wife do not like each other - the wife, without the slightest excuse, pounces on him. Once hit so hard that she left a scar. But even worse, she refers to their common child.
Somehow, the nurse left the baby alone for a few minutes, and when she returned, she saw her mother bite her teeth into the neck of the child, so that blood flowed from the wound. The nurse wanted to call for help, but the woman asked not to tell anyone and even paid for silence. The terrified maid began to monitor the child day and night, but the mother also watched him.
Unable to stand it, the nurse confessed everything to Fergusson, who decided that it was the fruit of her sore imagination, but then a child cried out. They rushed into the room and saw that there was blood on the baby’s sheet, and her mother’s lips were bleeding from her mother’s bed.Mr. Ferguson locked his wife, who refused to give any explanations, considering her a vampire, and he asks the great detective to come to his estate and sort out the situation.
Arriving at Mr. Ferguson’s home in Sussex, Holmes sees collections of South American utensils and weapons. He also draws attention to the spaniel, who fell ill with meningitis four months ago. Holmes comes into the room to Mrs. Ferguson. A woman has a nervous breakdown due to the inability to see the child. Having met with the children of Mr. Ferguson and his servants, Holmes writes a sick note asking for a meeting.
Dr. Watson, Holmes and Mr. Ferguson come to her room. Holmes removes all suspicions from a woman, considering the stupidity of the charge of vampirism. The woman was afraid for the child and sucked poison out of the wound. She was afraid to discover the truth, since the culprit was Jack, who hates his stepmother and is jealous of his father for his new wife and little son. Before injecting the baby with a poisonous needle, which he took from a collection of weapons, Jack tried the poison on a spaniel.
The great detective advises Mr. Fergusson to send Jack on a trip, and gives the husband and wife the opportunity to sort things out themselves.
