Persistence

It was probably better to interrogate them then and there, away from the people aboveground, but looking at them staring at the dead bodies all around them, it seemed like the interrogation wouldn't progress as quickly.

Thus they headed aboveground, into the dud house that acted as an entrance to this underground facility. 

It would also save them the trouble of worrying about another ambush underground, as unlikely as that was.

Having finished walking up the stairs, Lihar and Murkato sat their five captives down and started interrogating them one by one. Lihar was in charge of keeping guard while Murkato asked the questions.

The four thugs, like the system said, were clearly lying. Since they spoke separately, it was easy to spot the inconsistencies in their stories. The only thing Murkato learned from the thugs was what that underground area was, the structure of Glass Crow and what their job was.