"The Adventure of Charles Augustus Milverton" is one of the 56 Sherlock Holmes short stories written by Sir Arthur Conan Doyle. It is one of 13 stories in the cycle collected as The Return of Sherlock Holmes and was published in 1904.
Holmes is hired by the débutante Lady Eva Brackwell to retrieve compromising letters from a blackmailer: Charles Augustus Milverton, who causes Holmes more revulsion than any of the 50-odd murderers in his career. Milverton is "the king of blackmailers" and he makes his living out of blackmail. He demands £7,000 for the letters, which would cause a scandal that would end Lady Eva's marriage engagement to the Earl of Dovercourt. Holmes offers £2,000, all Lady Eva can pay, but Milverton insists on £6,000. It is worth £2,000 to him to make an example of Lady Eva. Holmes resolves to recover the letters by whatever means necessary, as Milverton has placed himself outside the bounds of morality.
Holmes visits Milverton's Hampstead house, disguised as a plumber, in order to learn the plan of the house and Milverton's daily routine. He cultivates the acquaintance of Milverton's housemaid and even becomes engaged to marry her. This rather shocks Watson, but Holmes assures him that he has a hated rival who will step in when the plumber disappears. Holmes has learned where Milverton keeps his blackmail papers (a safe in his study), and plans to burgle Milverton's house that night. Watson comes along.
They break into the study, and Holmes opens the safe. But just then Milverton, who should be in bed asleep, enters the study. Holmes and Watson hide behind a curtain, while Milverton has a midnight meeting with a supposed maidservant offering to sell letters that would compromise her mistress.
The woman is actually one of Milverton's former victims, whose broken-hearted husband died after Milverton revealed her secret to him when she refused to pay. She blames Milverton for his death, and vows to protect others from the same fate. She avenges her husband by shooting Milverton to death, then stamps on his face before escaping.
Watson instinctively begins to rush out and stop the shooting, but Holmes restrains him. Holmes understands, and Watson instantly realises, "that it was no affair of ours; that justice had overtaken a villain..." The woman runs away, and Milverton's household is roused by the shots. But Holmes takes the time to dump all of Milverton's blackmail papers on the fire in the fireplace, despite the risk of being discovered and caught.
Then Holmes and Watson escape through the garden and over the wall. Watson has to kick himself free from a pursuer who has grabbed his leg.
The next morning, Inspector Lestrade calls at Baker Street to ask for Holmes' help in investigating Milverton's murder, which he ascribes to the two burglars seen escaping over the garden wall. He has a description of one of them: "a middle-aged, strongly built man-square jaw, thick neck, moustache..." Holmes calls that vague. "Why, it might be a description of Watson!" he says, which amuses Lestrade. But Holmes refuses Lestrade's request: "my sympathies are with the criminals, and I will not handle the case."
Later, Holmes recognises the face of the woman who killed Milverton. He shows Watson her photograph displayed in a shop-window among those of other celebrities. Watson recognises the name of her famous husband, but Holmes signals silence with a finger to his lips.
- The Woman in Green is a loose adaptation of this story. Milverton is replaced by Moriarty.
- The 1965 BBC series adapted the story quite faithfully.
- The story was loosely adaptated for the Granada series as "The Master Blackmailer".
- Elementary's "Dead Man's Switch" is a loose adaptation.
- Sherlock's "His Last Vow" uses elements of the story and has Charles Augustus Magnussen as an adaptation of the Charles Augustus Milverton character.