Fading Light

As Jon was deep in thought, he noticed that the light was fading. He jumped up off the closed coffin he was sitting on and ran towards one of the cracked walls. He strained to look through the largest crack, but he couldn't see anything. But given the evidence, he figured that it was the sunlight that was fading. It must have been late in the day. How long was he in that coffin? A few minutes later, the light had been cut by half, and Jon began to panic. He wasn't afraid of the dark. But he *did* want to *see*, especially now. As he tried to think up new ways of getting out of this stone prison, he suddenly heard a tapping noise. He followed it to the other coffin in the room. Was something alive in there?