The Farbett who went ahead to make the guards "not see" is already well out of sight and sound. The party moves along down the tunnel in the direction he went.
"Something's not connecting," says Betham. Asked what he means, he adds, "He said the guards were watching the airfield. This tunnel doesn't really go there. I wonder if he meant the supply node at the junction with the main tunnel. It's just a bit further down."
"Supply node?" wonders Pru.
"Underground storeroom," continues Betham. "Emergency supplies in case of a disaster."
Pru chuckles. "Assuming those Farbetts haven't knicked 'em!"
Just as she says this, there is a roar from further up the tunnel followed by a more humanoid-sounding scream and a few sharp, muffled reports.