The Caves of NightJohn Christopher
Five people entered the caves - three men and two women. They intended to spend the afternoon exploring the outer chambers and, when a sudden fall of rock cut off their return, only one of them understood at first what that meant.
If any way of escape existed it could only come out in a series of caves known to exist on the far side of the mountain. To reach it they would have to find their way through the long, intricate galleries of rock, twisting and ramifying under the whole range of mountains, where at any moment their way might end in an impassable crevice. At best they would undergo days of struggle and growing exhaustion with their little supply of food quickly running out. Worse even than the fear of starvation was the realization that, within a few days, their lamps would begin to fade and, one by one, to fail altogether. After that would come the brief flare of their few remaining matches, and then the darkness - the utter, terrible darkness of the earth's interior, in which they would be left groping their way towards a certain and horrifying death.
The Caves of Night tells with frightening realism the story of those five people; how they came together, the ties and conflicts between them, and what happened when, all other hope gone, they set out on their terrible journey.
Christoper Samuel Youd, a.k.a. John Christopher (1922-2012), was a British science fiction author. He is best known for The Tripods trilogy.