No, don't. Hmmm.... I'm gonna do some thinking aloud now, so there will probably be a lot of text.
Do we know what was in the back room? Where she was tied up, I mean. And before you get all sneaky on me and say you lost time thinking, [No offense. Like I said, I'm paranoid.] this isn't thinking. This is us getting an idea of what we already know. But he's in the main shop, right? And the sirens are some distance away. Can we guess about how far away? I say, if the sirens are close, go into the back room and investigate the nail. Maybe it leads to a trap door or something? If you're a detective's daughter, you should be able to tell. But if they're not, peek into the gift shop and see what the owner is doing. We'll decide from there, cuz after that there are a lot of "If ... then ..."s.