"Yeah, well I'm not the one who thought it'd be a good idea to come in here," Peter grouses. He can't hear anything other than the very slight echo of their own voices, but it's obvious when the TARDIS picks up on something outside his range of hearing. Following her gaze -- and then turning to look quickly behind himself as well before following it again -- he makes an assumption. "Shit," he breathes. "Can you hear it?"