The Outsider Test, 3. Conference with Scruff

Back in my ordinary clothes (Jeans and sweater, since you asked), I pushed open the door of my cosy little flat and went in, glad of the refuge the place provides for me.
"What happened?"
Scruff, my sixteen-year-old sister, stretched and yawned. She had been lying on the sofa with four of my cats, watching television.
"Lamont's dead."
"What did you kill him with?" was her immediate response. Like I said, she's my sister, and she knows me very well.
"I didn't. That's the worrying thing. I was outside on the fire-escape when someone else visited vengeance on him. He was beheaded in front of me."
"Wow!" Scruff jumped to her feet. "Was it the Green Man?" I saw the look in her eyes and smiled. Scruff's acted as chaperone for a couple of my dates with him - the ones where they'd let a teenager with masses of untidy black hair and dressed in baggy sweater and trousers into the restaurant. For the posh places we have to rely on Ms Madison. Sometimes we get both, which is great fun. Scruff enjoys needling Ms Madison. I shook my head.
"I wish it had been - then we could have gone to a nice bar I know in the area, and Ms Madison would never have known. No. this was someone who sounded like a little girl, but she looked..." I searched for the right words. "She looked like a ghost, a swirling black shape, like smoke. She's calling herself 'The Outsider', and she's pretty scary. You know, laughing, chanting nuresery rhymes. Oh, and she has glowing red eyes."
"The Outsider? And she beheaded Lamont?" Scruff was clearly fascinated. She's adjusting fairly well to my lifestyle. But then, she did go to a girls-only boarding school.
"Yes. I didn't see what with, but she killed him."
"So what now?"
"We have to find the Outsider. If she's on our side we'll benefit from knowing each other - that way we won't be treading on each other's toes on a daily basis. If she's not on our side, but she's really an assassin hired by one of Lamont's enemies, we have to stop her before she can kill someone who isn't such a vile villain as Lamont was."
"You're just curious," Scruff told me. I laughed.
"I can't keep anything from you, can I? Yes, I'm curious. But after all, I do dress like a cat!"
"Well, don't get killed," Scruff warned me. "You're the last family I've got in this country, and I don't want to be an American."
"I don't want to be dead just yet, so you've got a deal."
And so we began our quest to find the mysterious spectral figure that was
THE OUTSIDER.