Attracted by the dog's interest, Injun and Whitey went to him.
The bedding in the bunk heaved and rolled from side to side.

Whitey reached over rather fearfully and pulled down the upper blankets, and Slim was brought to view.

Not only was Slim bound and gagged, but a coat was tied around his head, to keep him from hearing.

In fact, about the only thing to show that the man was Slim was his black hands.
Injun and Whitey hastily removed the head covering and the gag, and Whitey eagerly asked what had happened.

Slim was half choked and very indignant.
"I dunno what happened to nobody, 'ceptin' to me," he gurgled.