Here's a short story:

CHAPTER XXIV 

THE SEARCH FOR THE MISSING BOY 

"Tom isn't here!" 

It was Dick who uttered the words, as of a sudden he wheeled around on the dark trail and tried to penetrate the blackness of night behind them. 

"Isn't here?" demanded Jack Wumble, while Sam set up a cry of dismay. 

"No. Tom! Tom!" 

Sam joined in the cry, and so did the old miner, but as we already know, it was useless. 

"This is the wust yet!" growled Jack Wumble. "I told ye all to keep close to me." 

"Perhaps he fell asleep-- I know he was dead tired," answered Dick, hitting the plain truth. 

"We'll have to go back for him," said Sam, and turned without delay, for going ahead without Tom was all out of the question. 

"Yes, we'll go back," rejoined the old miner. "But go slow, or you may make matters wuss. I kin follow a clear trail, even of three hosses, but I can't follow a trail mixed up backward an' forward." 

They rode back slowly until at least half a mile had been covered. Then they shouted, but only a dismal echo came back. Dick fancied once that he heard Tom calling, but was not sure. 

Daylight found them still searching around, Dick and Sam with more sober faces than they had worn in many a day. They knew only too well the danger of becoming lost in those wild mountains. 

"Perhaps he has fallen in with Baxter's party," suggested Dick, as they came to a halt at the edge of a cliff overlooking a rushing river far below. It was past the breakfast hour, yet none of them felt like eating.  (End of story)

Provide your best guess for the following question. Give ONLY the guess, no other words or explanation.

For example:

Guess: <most likely guess, as short as possible; not a complete sentence, just the guess!>

Here are a few examples of questions and answers:

Question: Who was looking for Tom?
Guess: Dick

Question: Any idea why?
Guess: lost

Question: Where were they?
Guess: mountains

Question: Was Tom asleep?
Guess: Perhaps

Question: Why do you say that?
Guess: Perhaps he fell asleep answered Dick

Now answer the following question in the same format.

Question: Any reason he thought that was a possibility?

he was dead tired