From the first he had not the slightest doubt of it.

Somebody, some traitor in the Union camp, knew the nature of his errand, and was hanging on to the pursuit like death.
Dick knew it was the little man whom he had seen by the river, and perhaps the canoemen were with him--he would certainly have comrades, or his own danger would be too great--and they had probably obtained the bloodhounds at a farmhouse.

Nearly everybody in Mississippi kept hounds.
The long whining note came again and much nearer.

Now all music was gone from it for Dick.

It was ferocious, like the howl of the wolf seeking prey, and he could not restrain a shudder.