Cedric followed Fiona into the tunnel...
It was dark inside and the entrance behind them closed once they passed through. The darkness of his surroundings didn't really bother Cedric, and it seems that it doesn't bother Fiona either.
They continued walking in silence until they arrived at a fairly lit area of the tunnels. There, Cedric saw a massive formation blocking the way. His brain immediately went into analytical mode as he dissected that formation.
It was fairly complicated but it does one major thing, and that is to block the way of any unauthorized people, preventing them from going any further.
"Stand beside me," Fiona ordered, which Cedric followed.
They then walked up to the formation and all of a sudden, Cedric heard:
"Please stand still for identity verification."