Sort of an Alternate Universe story, in which the boys and their office are trapped for over a century in a block of concrete and must find a way to live without outside contact for the rest of their lives.
In this sort of "alternate universe" story, Grame agrees to help the government on a new construction project. But the boys' office gets covered in a thick layer of concrete and they cannot get out. The rest of the episode details over 100 years as the boys struggle with loneliness, religion, personality clashes, hunger, and aging without any contact with the outside world.—E. E. Buchanan