In The Illustrious Client, there is no clearly defined 'crime’ technically, it’s more about Baron Gruner coercing Violet de Merville (I think she’s the fourth Violet in the canon) to marry him. This is how the client describes Gruner:
“The fellow is, as you may have heard, extraordinarily handsome, with a most fascinating manner, a gentle voice, and that air of romance and mystery which means so much to a woman. He is said to have the whole sex at his mercy and to have made ample use of the fact.”
Don’t let this fool you, he’s not the next tumblr sexyman since he was quite literally accused of killing his old wife and managed to get away with it.
Gruner was already on Sherlock’s radar, and he knew about his background before the client explained. The client wanted to convince Violet not to marry Gruner, so she wouldn’t be in danger, but that didn’t work and so Sherlock was called in. To get an idea of this guy, he is compared to the likes of Moriarty and Sebastian Moran.
“We are dealing on this occasion, Mr. Holmes, with a man to whom violence is familiar and who will, literally, stick at nothing. I should say that there is no more dangerous man in Europe.” “I have had several opponents to whom that flattering term has been applied,” said Holmes with a smile... “If your man is more dangerous than the late Professor Moriarty, or than the living Colonel Sebastian Moran, then he is indeed worth meeting.”
At the same time, Gruner is also described as being a man of intellectual hobbies, so it’s difficult to understand what his character is.
“He has expensive tastes. He is a horse fancier. For a short time he played polo at Hurlingham, but then this Prague affair [when he murdered his wife] got noised about and he had to leave. He collects books and pictures. He is a man with a considerable artistic side to his nature. He is, I believe, a recognized authority upon Chinese pottery and has written a book upon the subject.”
Violet refuses to listen to anyone’s advice and is practically entranced by Gruner. I don’t know what magic powers this man has, because he told her about his past and she still wanted to be with him, but Sherlock believes he’s managed to brainwash Violet. Maybe Violet has a thing for Chinese pottery.
Sherlock visits Gruner, to try to convince him to break off the engagement, but it’s almost like Sherlock fell under the spell as well.
[Sherlock] “He is an excellent antagonist, cool as ice, silky voiced and soothing as one of your fashionable consultants, and poisonous as a cobra. He has breeding in him–a real aristocrat of crime, with a superficial suggestion of afternoon tea and all the cruelty of the grave behind it. Yes, I am glad to have had my attention called to Baron Adelbert Gruner.” [Watson] “You say he was affable?” “A purring cat who thinks he sees prospective mice. Some people’s affability is more deadly than the violence of coarser souls.
Side note: Sherlock tends to talk this way about most of his opponents who, although he doesn’t like them, he still feels impressed by them.
Unfortunately, he gets nowhere.
‘I [Gruner] rather thought I should see you sooner or later, Mr. Holmes...My dear man,’ said he, ‘you will only ruin your own well-deserved reputation. It is not a case in which you can possibly succeed. You will have barren work, to say nothing of incurring some danger. Let me very strongly advise you to draw off at once.’ “ ‘It is curious,’ I answered, ‘but that was the very advice which I had intended to give you. I have a respect for your brains, Baron, and the little which I have seen of your personality has not lessened it. Let me put it to you as man to man... It would not be pleasant for you if these facts of your past were brought to her notice.’ “The Baron has little waxed tips of hair under his nose, like the short antennae of an insect. These quivered with amusement as he listened, and he finally broke into a gentle chuckle. “ ‘Excuse my amusement, Mr. Holmes,’ said he, ‘but it is really funny to see you trying to play a hand with no cards in it. I don’t think anyone could do it better, but it is rather pathetic, all the same. Not a colour card there, Mr. Holmes, nothing but the smallest of the small.’ “ ‘So you think.’ “ ‘So I know. Let me make the thing clear to you, for my own hand is so strong that I can afford to show it. I have been fortunate enough to win the entire affection of this lady... You have heard of post-hypnotic suggestion, Mr. Holmes? Well, you will see how it works, for a man of personality can use hypnotism without any vulgar passes or tomfoolery. So she is ready for you and, I have no doubt, would give you an appointment... “ ‘By the way, Mr. Holmes,’ said he, ‘did you know Le Brun, the French agent?’ “ ‘Yes,’ said I. “ ‘Do you know what befell him?’ “ ‘I heard that he was beaten by some Apaches in the Montmartre district and crippled for life.’ “ ‘Quite true, Mr. Holmes. By a curious coincidence he had been inquiring into my affairs only a week before. Don’t do it, Mr. Holmes; it’s not a lucky thing to do. Several have found that out. My last word to you is, go your own way and let me go mine.’
It was difficult to cut that down so I’m not posting massive extracts from the book, but Baron Gruner and Sherlock’s meeting was full of good dialogue that really emphasise how uncomfortable Gruner makes people. What is most scary about him is that there are real men like him who can gaslight women in to turning against their entire families and then hurting them. For a book written in the 19th century, it’s surprisingly revealing and isn’t at all like how Gruner could have been romantacised in other novels.
Kitty Winters is another woman whom Gruner took advantage of, and she tells Sherlock about one of his books.
“It’s a book he has–a brown leather book with a lock, and his arms in gold on the outside. I think he was a bit drunk that night, or he would not have shown it to me.” “What was it, then?” “I tell you, Mr. Holmes, this man collects women, and takes a pride in his collection, as some men collect moths or butterflies. He had it all in that book. Snapshot photographs, names, details, everything about them. It was a beastly book–a book no man, even if he had come from the gutter, could have put together. But it was Adelbert Gruner’s book all the same. ‘Souls I have ruined.’”
Gruner literally hunted women for sport and then documented it, like their lives were just trophies.
Watson later meets Gruner, and we get yet another lengthy description about how good-looking he is: even Watson can’t help himself.
“He was certainly a remarkably handsome man. His European reputation for beauty was fully deserved. In figure he was not more than of middle size, but was built upon graceful and active lines. His face was swarthy, almost Oriental, with large, dark, languorous eyes which might easily hold an irresistible fascination for women. His hair and moustache were raven black, the latter short, pointed, and carefully waxed. His features were regular and pleasing, save only his straight, thin-lipped mouth. If ever I saw a murderer’s mouth it was there–a cruel, hard gash in the face, compressed, inexorable, and terrible. He was ill-advised to train his moustache away from it, for it was Nature’s danger-signal, set as a warning to his victims. His voice was engaging and his manners perfect. In age I should have put him at little over thirty, though his record afterwards showed that he was forty-two. “
But, this is all just a facade, as the end of the description says.
Hate Gruner yet? Lucky enough for you, Kitty Winters gets revenge and throws acid in his face! His face basically melts off, and I’m not sure if he survives, but at least it’s the end to him hunting and destroying lives.