As luck and/or coincidence and/or contrivance would have it, someone is within earshot of such a knock. This someone hasn't been waiting, really... in fact, he's just finished releasing another arrival from another cell, and when this mysterious so-and-so comes rapping at the chamber door, he rolls his eyes and mutters Jesus Christ well under his breath. "Just a second," then, sounding more charitable. It's not whoever's fault that they've showed up here, after all. He's just destined never to get back to the front desk. Ever.

Now closer to the door: "If I open this, are you gonna rip my face off?"