"Oh, I love that!" she exclaimed. It made so much more sense that random people just meeting in the street. And it would mean that Isis' old-lady dress and walking stick and Trudy's cute little pigtails immediately looked right to the audience, rather than them wondering whether they were just dressed up in crazy costumes. She hunched over a little more and said "Yes dear, I really need to get him a new leash, or find a better charm for this one..." she looked at the supposed dog lead and sighed, then added "You're such a good girl dear, helping me find him. Where do you think he could have gone?"
She straightened up "and then maybe you could say you heard a dog barking, and point to the house and we can talk about how it's supposed to be haunted...oh! Maybe I could say something like 'when I was a girl, there was a beautiful woman lived there on her own, but she had no friends . Nobody ever went in or out. I wonder what happened to her'" and you say that you'd heard stories about it being haunted...that might work? Like, if you believe in ghosts and I don't, but I see the ghost?" Isis thought that might be quite a fun way of introducing the idea of the house being haunted. It didn't entirely make sense, because Trudy had clearly met and chatted with ghosts, and presumably everyone could see them...but perhaps some no-majs could see ghosts and others couldn't? They could alway say they were pretending to be no-majs if anyone asked afterwards, she supposed...
She listened to Trudy's ideas, pleased with how this was taking shape. So she came running out - well, running as fast as an old lady
could run, unless she dropped her character for a moment, ran screaming and then pretended to realise she'd done something wrong... No. The idea amused Isis but not everyone shared her sense of humor and she didn't want them to think she'd forgotten her character. "So I run out screaming, but I realise you're still there, so I have to go back in, and I call your name, but instead he ghost answers..?"
"That's perfect! I'm an old lady, so I'd have time to go and visit the ghost and be friends with it!" The thing with the dog was a bit awkward though, If they were using a plushie they could hardly expect it to act a role, and without their wands they would even be able to make it levitate across the stage. That was a pity - it would have been funny to do that. "Oh, how about this?" she suddenly thought "So at the end, after I've talked to the ghost, and I say what about my granddaughter and you say what about me? and you then come out of the house saying "Look, I found Scooter - and you can hold the plushie and it won't matter that it can't move or say anything..?"
Isis thought that all sounded great. Sure, the ending wasn't quite perfect yet, but they'd tied up all the loose ends and made a story, now they just needd to rehearse until they got it right.