If Whitey had been a dog, a goat, a fowl, or even a stray calf, they would have felt equal to him; but now that the earlier glow of their wild daring had disappeared, vague apprehensions stirred.

Their "good look" at Whitey had not reassured them--he seemed large, Gothic and unusual.
Whisperings within them began to urge that for boys to undertake an enterprise connected with so huge an animal as an actual horse was perilous.

Beneath the surface of their musings, dim but ominous prophecies moved; both boys began to have the feeling that, somehow, this affair was going to get beyond them and that they would be in heavy trouble before it was over--they knew not why.

They knew why no more than they knew why they felt it imperative to keep the fact of Whitey's presence in the stable a secret from their respective families; but they did begin to realize that keeping a secret of that size was going to be attended with some difficulty.

In brief, their sensations were becoming comparable to those of the man who stole a house.
Nevertheless, after a short period given to unspoken misgivings, they returned to the subject of the reward.