Mattie watches, but as she has no understanding of how the thing works, she can't possibly speculate on what exactly it is that he's doing. Still, the picture and voices appear to go away, so at least that much he was telling the truth about.

"I am sixteen." Said with all the haughty self-assurance of someone still walking that fine line between girl and woman. A gesture of openness requires the same in response, however, and so after a pause she adds, "My father is recently deceased. Murdered, in fact, by an ungrateful scoundrel by the name of Tom Chaney, and I am going to see that he is brought to justice."

There's a good possibility he already has. But she can't be certain until she returns to the place she was snatched from, and sees the evidence herself.