The story goes back in time to the day of the picnic.
Tom and Becky explored the cave with the group and played Hide and Seek until they got bored with it. They had read the graffiti on the wall. They wandered, not paying attention to where they were going. They mark their own names on the wall as well.
Tom becomes interested in exploring an area they come across. He leaves some markings to show the direction they went. They see many interesting natural features. They startle some bats, and one puts out Becky’s candle. The children flee to a passage that leads to a subterranean lake.
Becky gets worried when she realizes they can’t hear the others. Not wanting to encounter the bats, who may knock out their remaining candle, Tom proposes to take a different way back.
They get lost. Tom cries out, hoping the others will hear him. Becky becomes hysterical, and he comforts her. Tom feels terrible for getting them into this mess.
Tom uses the candle sparingly, realizing they can’t waste it. They keep moving. Finally, Becky is too tired to go further and falls asleep. When she wakes up, they walk some more. They imagine more time has elapsed than it has.
Tom finally decides they need to stay where there is water. They are down to their last candle. Becky is frightened but is certain people are looking for them. The candle goes out. Becky becomes silent as time goes on, too depressed to talk. Tom tries to keep her hopes up.
One day, they hear far off voices. The voices grow fainter. The children tried to follow them, but they come across a pit. They return to the lake.
Tom ties some kite line to keep track of his direction as he explores new side passages. He encounters Injun Joe, who scrambles off.
The children are famished. Becky is getting weak. Tom explores another passage alone.