"Neither is a guy who sees 20/200," Dan replied, "but I wouldn't trust him to see past his own face."  Dan led the way.  "Okay, good news...it's not totally smooth, so my idea about this area being engineered is probably wrong.  Though I'm surprised, I didn't think that California-"  And then he stopped.  "Alex? Do you see that?"  He moved the flashlight over the doorway of stone.  "That is definitely man-made.  So...there probably have been people down here...but..."  Dan stepped forward a little bit.  "...that shouldn't happen."  He was, of course, referring to the fact that the flashlight didn't go into the darkness.  "Alex.  Gimme something out of your bag.  I want to poke at the portal, see if anything happens."  Dan wasn't going to risk losing the flashlight.  Once he had something suitable in hand, he pushed the tip of it through the darkness of the doorway.