Gryffindor Common Room; Open to all
Jack is in a disturbingly happy mood, he's also reading a book. This is worrying. He's looking things up, cross referencing. Trying to work things out. No-one is safe, not that they were before from him. He's starting off small, by small that means he's just sticking to the common room. Trying to find things that shouldn't be there. In theory if he pokes about long enough he's going to find something. Hidden passages he reasons must be around here somewhere and if he can find them. Map them out for himself, work on getting the whole castle done. Free run of the place. No-one would be safe. He's reading and poking at the wall right now, shouldn't be long til he gets somewhere.