"Oh god, what now," he asks the tunnels, feeling a cold sweat washing over him despite the warmth of the humidity down here.

Hey, omniscient narration? Please don't tell him it was a rumbling like a cave-in from, say, the direction he came from.

But if there's anything worse than venturing illegally into the tunnels on a lark because mice bullied him into it, it's doing all that and not even finding anything worthwhile. Might as well press on and hope he learns to teleport or something.