OH HOLY SHIT GUYS. (Also, yeah we all know that Plot A and Plot B will merge, shut up)
Plot A: Pitt is called in to investigate the murder of a sketchy-ass usurer named Weems, who was shot in his own house (the ME figures out that someone loaded a big ol' gun with GOLD COINS and BLASTED HIM IN THE FACE WITH IT, after he recovers a gold coin from dude's BRAIN). Weems doesn't even live in Pitt's jurisdiction. Pitt's boss, Micah Drummond, is particularly hoping to clear a friend, Lord Byam, of the murder. He's secretive about it, which makes Pitt nervous. Pitt locates two lists: one is of poor people who borrowed money from Weems and were paying it back, but would never finish because Weems is a fucking asshole. The other list contains names from the aristocracy, but NOT Byam, along with amounts of money, presumably how much they borrowed. But Pitt figures out that they didn't, since they would never have gone to Weems; instead, Weems is likely blackmailing them. On his list are:
Lattimer, a Scotland Yard cop who bets on bare-knuckle fighting (which is illegal) and makes good money for it
Urban, a cop near Pitt's own jurisdiction, who has a taste for fine art and finances it by being a bouncer at some music halls (which he'd be fired for, if his bosses found out)
Carforth, a judge who appears to be dating Fanny Hillard, a girl about his eldest daughter's age, though he's married; it turns out that she's actually his secret daughter (which I guessed) from his first and only legitimate marriage (which I did NOT guess); Carforth's current marriage is bigamous, so his "public" children are illegitimate
and like maybe one more person but I don't remember. Byam's actually being blackmailed with half a letter that was written to him by Lord Anstiss's late wife Laura, who was beautiful and fragile and apparently very impulsive. According to Byam, he flirted with Laura but never actually went any further, and when he told her that he couldn't be with her, she killed herself. Byam's wife knows about it, and since it was a long time ago, she's basically forgiven him for it.
(And let me just say that the blackmail scenario just didn't sound right to me. I suspected everything about it, because it was a letter found among Laura's things, which would mean it hadn't been sent, and I thought that maybe it was forged, maybe it was written to someone else, maybe it didn't exist... anyway.)
Plot B: Emily's new husband Jack is standing (running for) Parliament, but Emily's pregnant, so Charlotte's kind of filling in for her as hostess and running dinner parties, etc. Jack's trying to earn the patronage of Lord Anstiss, who is friends with Lord Byam (despite the aforementioned "Anstiss's wife killed herself over her infatuation with Byam" problem). Lord Anstiss is currently backing "Fitz" Fitzherbert, who is like quasi-engaged to Odelia Morton, who is really pretty and very proper and very well dressed. Charlotte likes Fitz even though she doesn't want to, because of course Fitz is against Jack. Then Fitz sees Fanny Hillard at a party and they really hit it off.
So:
-Charlotte becomes friends with Fanny, finds out about her situation, talks to Carforth and gets his side of it, and advises Carforth to come clean with Fitz just so he can marry Fanny without the specter of "she was totes a slut" in the air
-Micah Drummond called Pitt in because of the shady secret society he's a member of, the Inner Circle. The Inner Circle helps this jackass who was feeling up a sexually provocative woman in a public park - the cops catch them "partially dressed" and fooling around, and bring them in to charge them with public indecency, but the case goes before Carforth, and Carforth dismisses it for lack of evidence. It's clearly ridiculous because there's plenty of evidence, but someone thinks it's appropriate to use influence to have the case dismissed, even though it's minor. So said lecherous jackass is a member of the Inner Circle, as are the other people on the blackmail list. It's okay, though, cause he does it again and is caught dead to rights this time.
-Eventually Pitt figures out that the second list, the high-class blackmail list, actually corresponds to "people the Inner Circle wants to punish by dragging their names into a murder case."
-Micah totally falls for Byam's wife, and she for him, so I knew that Byam would likely die by the end of the book. Even after Weems is dead, Byam's still upset, and Byam's wife tells Micah that he's still being influenced by someone who is causing him to make strange/unaccounted-for decisions in Parliament, since he's in the Treasury department. The assumption is that someone went through Weems's things, found the Byam letter, and took it and any other reference Weems had to Byam, and is now using that to blackmail Byam.
They keep going back to: why would Weems have sat still and let someone plug him in the face with a gun full of gold coins? And I thought, "To cover up another cause of death. That's why he sat still; he was already dead."
Lord Anstiss, after he cuts Fitz off for wanting to marry Fanny, offers Jack membership in a "really totally awesome secret society," and Charlotte's like "TELL HIM TO FUCK OFF" because Pitt's shared his own anger over the Inner Circle he's been discovering. Also Charlotte and Pitt meet Peter Valerius, who seems like an awesome guy (also socialist-ish).
Eventually Pitt and Drummond figure out that Anstiss is behind the current influencing of Byam, which means he likely killed Weems; they think it's for his threatening to reveal the "pre-suicide note" from Anstiss's wife/Byam's flirtation with the wife, which was 20 years ago. They bust into his house, find the murder weapon (a bloodstained walking stick), and go upstairs and break down his bedroom door:
AND FIND BYAM AND ANSTISS NAKED ON THE BED, BOTH DEAD. BYAM CUT ANSTISS'S THROAT AND THEN SLASHED HIS OWN WRISTS. HOLY SHIT.
Because that (unsigned) love note wasn't from Laura, IT WAS FROM ANSTISS, and YEAH GUESS WHAT BITCHES BYAM WASN'T HAVING AN AFFAIR WITH THE WIFE, IT WAS WITH THE HUSBAND. Byam leaves a suicide note for Pitt saying that Anstiss's wife, uh, found out (hence the note that was in HER things) and they had to kill her and fake a suicide (HOLY SHIT, tbh I doubted that she HAD committed suicide but DAMN). Weems tried to blackmail Anstiss with the half of the love note, and apparently figured out its actual significance, so Anstiss killed him and then tried to cover it up. Byam went out in that display of gay pride knowing that it would be notorious and people would comment on it, to get back at Anstiss for being such a total dick and blackmailing him like he did, because that broke his heart. Anstiss was making a lot of money by influencing Byam's financial decisions as he did.
Again I say, DAMN. And I hope Micah ends up with Lady Byam 'cause girl did NOT deserve that level of crazy to end her marriage, and it makes me wonder if Byam was bi or gay, if she'd figured out that he just wasn't into the ladies or what.