Arrin leads Fiona, Tommy, Bowen through the tunnels in promise of getting them on the other side of the wall. Before this, members of the black market were tracking them down so Arrin, Fiona, Tommy, and Bowen had to climb down the elevator shaft, into the tunnels to escape. While walking, Fiona feels that something is wrong but she doesn't know what.
After walking through the tunnels for over and hour, Fiona hears the faint noise not far in front of her that makes her more nervous. Then, Arrin suddenly disappears into the darkness of the tunnel ahead.
Tommy lights a match and they realize that Arinn had been leading the three of them into a trap the whole time. This scene is important because the readers learn through the situational irony that Arinn had been working for the men who run the black market the whole time and she was only helping Fiona so she could capture her and get paid.