Does anyone know the name of this childrens' book?

There was a book I read when I was younger and loved, but I can't remember the name! All I remember is it was about a girl who moved to a new area and met one of her neighbors ( a boy her age) or it could be the opposite way around - a boy who moved, yada yada yada...they find a clubhouse in like, an old antique shop maybe? And they have a bust of Queen Nefertiti they set up as the centerpiece. And the old shopkeeper watches them secretly too, I believe. Any ideas??