Partially sealing yourselves up in the cave for the night, your sleep is fitful at first, as you fear the approach of things hidden by the sound of the rolling waves outside.
After a while with nothing to worry about, you eventually fall fast asleep. The exertion of the day has been enough to ensure your sleep is deep, once it comes.
While Robert sleeps, you begin trying to find a way through the large metal door in order to gain access to the bunker. After trying to think of a way through it that doesn't involve explosives, which would have an extremely negative effect on your makeshift campsite, Jericho eventually decides to dig under the wall.
After excavating for a while, Jericho breaks through to the other side of the wall...or at least believes he does...as a cloud of trapped gas billows out from the hole Jericho has dug, making him momentarily lightheaded...what was that stuff? After a short while, Jericho manages to enlarge the hole enough that he can crawl through it and to the other side of the steel wall. Doing so, he discovers a pitch black room with an identical metal door at the far end, almost as if this section of cavern hallway was sealed off between the two steel doors. Seeing as how well the plan worked last time, Jericho retrieves some excavation tools and a light source, heads back to the newly discovered chamber, and begins digging under the second steel wall.
About the time Jericho has created a sizable pit under the second wall, he hears Robert, who must have just woken up, on the other side of the first steel wall, calling for him. "Jericho? JERICHO?? Where are you?"
Turning back to look over his shoulder in the direction of the chamber in which he left his partner, Jericho sees rays of blinding white light enter his antechamber. It seems to be coming from the chamber where he left Robert, entering this room from the small tunnel he excavated to enter this chamber. Whatever is producing that much light can't be a natural occurrence...