Two boulder-filled tunnels view the water I crossed, and after stooping to enter the low chamber, I see a steel door with a small panel next to it. Off to the side, another small chamber is just visible by the light of my candle. As I move farther into the room, the girl comes out from behind some boulders and points to the door. "I think this is it! Do you know the code?"

Take stepping stones out over the water.
Look closer at Door Panel.
Check the small chamber off to the side.