When Inaaya gets back she tells Joan about everything, because she always tells her Joan about everything, and Joan has extremely predictable opinions on deciding to talk to an incredibly dangerous murderer which are that Inaaya should not do it, and then on the third Inaaya sets herself to Figuring Out What The Hell Is Going On Here.

Which, due to her very particular combination of skills, means she figures out where the Roby mansion is, so that she can go there and find out if they have cats.

​​The house at 4, Curzon Street, Mayfair is a fine Georgian mansion standing in a walled and gated garden, with a stray cat outside licking his paw.

Oh good that's so helpful. "Hi!" she says to the cat.

"Hi!"

"How long have you been living near this house?"

"Since I was a kitten."

"Oh good! Do you know the humans who live here?"

"They don't give milk! They secure all the doors and the windows all the time because they don't like it when cats get in." He sniffs. "Like I would try to enter their milkless house anyway."

"Terribly ungiving of them," Inaaya says agreeably.

"Why do you ask?"

"Two years ago two people were killed there, and nobody knows how it could possibly have been done, and I figured, well, probably nobody had asked the cats."

"Oh, I saw the bodies. They left the door open so I went inside to see what they'd been hiding from me all this time."

"........oh?"

"The bodies were in that room." He indicates one to the left of the door. "Really horribly mutilated."

"Mutilated how?"

"All torn apart like by a human with giant claws."

...yeah, that's consistent with what Valentine said happened to the nurse who may or may not have been killed by the devil.

(Roby confessed to the murders-- but Valentine isn't trying to argue to anyone except random visitors who speak Polari that it wasn't her-- but also Inaaya is pattern-matching and she doesn't actually have nearly enough evidence to start making predictions like that one.)

"Huh," she says, in lieu of that, "that's weird and interesting."

"They kicked me out," the cat says, incredibly offended.

"Terrible."

"I heard an awful whistle the night before," the cat says. "And about five minutes later there was this incredible racket from the house. Couldn't sleep at all. Must have been the sound of people being murdered."

...aaaaand of course Dr. Aarons is a day's train ride away. Well, she can write and ask if there were weird whistling noises on the night of October 31st. "What was the whistle like?"

"Ear-piercing and horrible? Very shrill. One of the nasty humans found a whistle and blew it and it made the same sound. Why would they do that?"

"Because it makes such a loud noise it's a very quick way of getting the attention of everyone nearby."

The cat looks VERY SUSPICIOUS ABOUT THIS CLAIM.

"I don't like it either but that's why police and similar people use them."