It did not take long for the cat to find the stairs and come up to see what was up here. Then he vanished into Julie's room. Then he just vanished.
Eventually, this became a problem, because Gretchen *really* needed to come in, but the cat could not be found and we didn't really want to abandon Ruby outside. But necessity is a mother (or something like that), so Ruby was locked in her kennel until Skeezix/Buddy decided to wander back out of Julie's room where he could be corralled and returned to the library.
He is a *very* sweet kitty.
So far, so good.
(And we are looking for a pet gate for the library door.)